Automotive Power Supply System

ABSTRACT

An automotive power supply system comprises a battery module that includes serially connected battery groups each constituted with serially connected battery cells, integrated circuits each disposed in correspondence to one of the battery groups, a control circuit, a transmission path through which the integrated circuits are connected to the control circuit and a relay circuit via which an electrical current is supplied from the battery module. In response to a start signal instructing an operation start and received via the transmission path, each integrated circuit measures terminal voltages at the individual battery cells in the corresponding battery group and executes an abnormality diagnosis. If abnormality diagnosis results provided by the integrated circuits indicate no abnormality, the control circuit closes the relay, enabling supply of electrical current from the battery module and subsequently, the control circuit receives measurement results from the integrated circuits via the transmission path.

INCORPORATION BY REFERENCE

The disclosure of the following priority application is hereinincorporated by reference:

Japanese Patent Application No. 2007-253649 filed Sep. 28, 2007

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automotive power supply system.

2. Description of Related Art

There are automotive power supply systems known in the related art thatinclude an inverter connected to a rotating electrical machine and amulti-series battery control system.

Such an automotive power supply system is configured so as to charge theindividual batteries in the multi-series battery control system, whichare connected in series, via the inverter with the power originatingfrom the rotating electrical machine that rotates as the vehicle travelsand also to supply power from the batteries to the rotating electricalmachine via the inverter.

The voltages at the individual batteries are detected and the SOC (stateof charge) of each battery is adjusted so as to equalize the voltagevalues at the various batteries in the multi-series battery controlsystem. The serially connected batteries and an electrical load such asthe inverter in the automotive power supply system are connected witheach other via a relay circuit.

An automotive power supply system assuming the structure described aboveis disposed in, for instance, Japanese Laid Open Patent Publication No.2005-318751.

While it is desirable to supply power to the electrical load as soon aspossible in the automotive power supply system structured as describedabove, there is a safety issue yet to be addressed effectively in thatin the event of an abnormality at a battery power may be supplied beforethe abnormality is detected.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an automotive powersupply system assuring a high level of safety.

The object described above is achieved in the present invention byproviding an automotive power supply system comprising a battery modulethat includes a plurality of serially connected battery groups eachconstituted with a plurality of serially connected battery cells, aplurality of integrated circuits each disposed in correspondence to oneof the battery groups, a control circuit, a transmission path throughwhich the integrated circuits are connected to the control circuit and arelay circuit via which an electrical current is supplied from thebattery module. In response to a start signal instructing an operationstart and received via the transmission path, each integrated circuitmeasures terminal voltages at the battery cells in the correspondingbattery group and executes an abnormality diagnosis. If abnormalitydiagnosis results provided by the integrated circuits indicate noabnormality, the control circuit closes the relay, enabling supply ofelectrical current from the battery module and subsequently the controlcircuit receives measurement results from the integrated circuits viathe transmission path. Since this structure allows the abnormalitydiagnosis to be executed with priority, power can be supplied quickly.

Another automotive power supply system according to the presentinvention comprises a lithium battery module that includes a pluralityof serially connected lithium battery groups each constituted with aplurality of serially connected lithium battery cells, a plurality ofintegrated circuits each disposed in correspondence to one of thelithium battery groups in the battery module, a transmission paththrough which the integrated circuits are connected and a relay viawhich power is supplied from the lithium battery module. The integratedcircuit cyclically generates a stage signal to be used to specify ameasurement target lithium battery cell in response to an operationstart signal. The integrated circuit includes a selection circuit thatselects the measurement target lithium battery cell in the lithiumbattery group corresponding to the particular integrated circuit basedupon the stage signal, an analog/digital converter that converts aterminal voltage at the lithium battery having been selected by theselection circuit to a digital value, a digital comparator circuit thatcompares the digitized terminal voltage value with an over-chargediagnosis threshold value and a transmission circuit that outputs anabnormality signal indicating an abnormality based upon comparisonresults provided from the digital comparator circuit and includes aone-bit signal transmission terminal used to transmit the abnormalitysignal, a one-bit signal reception terminal, a serial transmissionterminal and a serial reception terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the structures adopted in the battery moduleand the cell controller in the automotive power supply system achievedin an embodiment of the present invention;

FIG. 2 is a block diagram showing an integrated circuit structure thatmay be adopted in the automotive power supply system according to thepresent invention;

FIG. 3 illustrates the communication command transmission/receptionmethod adopted in the integrated circuits in the embodiment;

FIG. 4 illustrates an example of timing with which the measurementoperation may be executed;

FIG. 5 illustrates a circuit via which measurement operation to beexecuted in correspondence to the number of battery cells, is enabled,as achieved in an embodiment;

FIG. 6 illustrates a diagnosis target circuit and a circuit engaged inthe diagnosis, as achieved in an embodiment;

FIG. 7 shows a communication circuit, which is installed within eachintegrated circuit and is engaged in communication command exchange, asachieved in an embodiment;

FIG. 8 presents an example of a procedure through which the addressregister may be set for each integrated circuit based upon acommunication command;

FIG. 9 illustrates the operation executed at the communication circuitin response to transmission of a communication command;

FIG. 10 illustrates the procedure through which addresses aresequentially set at the individual integrated circuits based upon thecommunication command;

FIG. 11 presents a flowchart of an example of processing through whichthe state of charge at each battery cell is measured and any batterycell indicating a large charge quantity is discharged;

FIG. 12 presents a flowchart of an example of processing through whicheach integrated circuit or each battery cell is tested for abnormality;

FIG. 13 is a circuit diagram presenting an application example in whicha DC power supply system is adopted in a drive system for an automotiverotating electrical machine;

FIG. 14 presents a flowchart of an example of an operation that may beexecuted in the automotive power supply system in FIG. 13;

FIG. 15 presents an example of the sequence through which communicationbetween the battery controller and the cell controller is terminated;

FIG. 16 presents another example of the sequence through whichcommunication between the battery controller and the cell controller isterminated;

FIG. 17 shows an embodiment that includes battery groups made up withvarying numbers of battery cells;

FIG. 18 is an external view of a battery module;

FIG. 19 shows the internal structure of a battery module;

FIG. 20 is a plan view presenting an example of a cell controller builtinto a battery module;

FIG. 21 presents an example of a circuit structure that may be adoptedto enable both balancing switch control and individual battery cellterminal voltage measurement;

FIG. 22 presents another example of a circuit structure that may beadopted to enable both balancing switch control and individual batterycell terminal voltage measurement;

FIG. 23 is an operation diagram illustrating the relationship betweenthe measurement control and the discharge control executed for SOCadjustment, observed in the circuit shown in FIG. 21;

FIG. 24 is an operation diagram illustrating the relationship betweenthe measurement control and the discharge control executed for SOCadjustment, observed in the circuit shown in FIG. 22;

FIG. 25 presents an example of a circuit that may be used to execute thecontrol shown in FIG. 23 or FIG. 24;

FIG. 26 presents an example of a diagnosis executed to detect anabnormality occurring at the detection harness;

FIG. 27 presents another example of a diagnosis executed to detect anabnormality occurring at the detection harness;

FIG. 28 illustrates a method that may be adopted to detect anabnormality in the electrical connection between the battery cells andthe individual integrated circuits in the structure shown in FIG. 26 orFIG. 27;

FIG. 29 shows a signal OFF period set via the discharge control circuitto give priority to the balancing switch control;

FIG. 30 shows a signal OFF period set via the discharge control circuitto give priority to the balancing switch control;

FIG. 31 presents another example of the diagnosis target circuit and thecircuit engaged in the diagnosis; and

FIG. 32 is a diagram showing the structures adopted in the batterymodule and the cell controller in the automotive power supply systemachieved in another embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The following is an explanation of an embodiment of the automotive powersupply system according to the present invention, given in reference todrawings. The embodiment of the present invention described belowassures a high level of safety in a drive system for an automotiverotating electrical machine, in a DC power supply system, in a DC powersupply cell controller or in integrated circuits used in a DC powersupply cell controller.

Through the embodiment described below, the following issues areeffectively addressed as well as the issues described earlier.

In the embodiment described below, a diagnosis for a connecting linethat connects an integrated circuit that measures a terminal voltage ata battery cell with the battery cell, as well as a diagnosis for thebattery cell itself, is executed. These two types of diagnosis areexecuted independently at each integrated circuit and in the event of anabnormality, the occurrence of the abnormality is reported via atransmission path to a higher-order control device, i.e., a batterycontrol device. The structure allows the diagnosis for the connectingline connecting the battery cell and the integrated circuit, as well asthe battery cell abnormality diagnosis, to be executed prior to powersupply to an electrical load such as an inverter. Since the relay is setin a continuous state and the power is supplied only if no abnormalityis detected through the two types of diagnosis, a high level of safetyis assured. In addition, since a plurality of integrated circuits eachautomatically executes the diagnosis in response to an operation startcommand, the diagnosis for all the battery cells and the connectinglines can be completed quickly, thereby allowing the power supply to theelectrical load to start promptly. Furthermore, since the integratedcircuits each automatically start the diagnosis, the higher-ordercontrol device does not need to issue individual commands, therebyreducing the control onus.

In addition, in the embodiment described below, a diagnosis for theintegrated circuits themselves is executed in addition to the diagnosisfor the battery cells and the relay is set in a continuous state tostart power supply only if no abnormality is detected through the twotypes of diagnosis As a result, a high level of safety is assured.

In the embodiment described below, the occurrence of an abnormality isreported to the higher-order device or the other circuits with a one-bitsignal, i.e., an abnormality flag, making it possible to transmit theabnormality signal without first receiving a transmission instructionfrom the higher-order side. Thus, the need for reporting an abnormalitythrough a simple mechanism is satisfied. It is crucial to accuratelydetermine whether or not an abnormality has occurred since thepresence/absence of an abnormality directly affects the judgment as towhether or not the system should shift into the next control. For thisreason, it is extremely effective to assure a function of firstreporting whether or not an abnormality has occurred through thetransmission path before reporting details such as the cause of theabnormality in a subsequent step. In the embodiment, serial transmissionand one-bit transmission, i.e., flag transmission, are used incombination and the presence/absence of an abnormality is quicklyreported through the one-bit transmission. If there is no abnormality,the operation shifts into a power supply start stage.

In the embodiment described below, as a given integrated circuitreceives a one-bit abnormality flag, it transmits a one-bit abnormalityflag to the next integrated circuit. If an abnormality is detected atthe integrated circuit itself, it transmits an abnormality flag to thenext integrated circuit. Namely, the integrated circuit transmits asignal indicating no abnormality to the next integrated circuit only ifit has not received the abnormality flag and it has not detected anabnormality. As a result, any state of abnormality can be promptlyreported to the higher-order control circuit, i.e., the battery controldevice.

In the structure adopted in the embodiment, a stage circuit within eachintegrated circuit cyclically generates a stage signal, the measurementtarget battery cell terminal voltage is selected in sequence based uponthe stage signal, the selected terminal voltage is converted to adigital signal via an analog/digital converter and the digital signal isused as a measurement value. The integrated circuit also has a batterycell diagnosis function that is engaged to execute diagnosis for thetarget battery cell based upon the digital signal indicating themeasurement results in response to the stage signal originating from thestage circuit. As described above, following the measurement of theterminal voltage at the battery cell, which is executed cyclically, thediagnosis for battery cell over-charge or the like is executed insuccession based upon the digital signal indicating the measurementresults. Since the target battery cell is selected cyclically in apredetermined order, the terminal voltage at the selected battery cellis measured and the over-charge diagnosis or the like is executed insequence by linking with the measurement operation, an abnormality canbe diagnosed quickly based upon the measurement value. Furthermore,since the measurement and the diagnosis are executed at each integratedcircuit over predetermined cycles, the diagnosis for all the batterycells constituting the battery module can be executed in a short periodof time, assuring a high level of reliability.

In the embodiment, a selection circuit selects a specific voltagegenerated inside each integrated circuit independently of the terminalvoltage measurement and conversion results obtained by converting theselected voltage through the analog/digital converter, are compared withthe threshold value to determine whether or not the conversion resultsand the threshold value sustain a known relationship. If an abnormalityoccurs in the selection circuit or the analog/digital converter, theknown relationship will no longer be sustained. Namely, the internaldiagnosis for the integrated circuit can be executed based upon therelationship.

In the embodiment described below, the terminal voltage at each batterycell is cyclically detected and the average of a plurality ofmeasurement values obtained by measuring the terminal voltage aplurality of times is used as a measurement value. When the electricalload is an inverter, there is bound to be significant noise. Under suchcircumstances, the detection accuracy can be greatly improved by usingthe average of a plurality of digitized values. In addition, thestructure in the embodiment includes a hardware averaging processingcircuit disposed at a stage rearward of the analog/digital conversioncircuit so as to reduce the onus placed on the software. A digitalcomparator circuit is disposed at a stage further rearward relative tothe averaging processing circuit, so as to realize an automatic noiseremoval function at each integrated circuit and thus maintain a highlevel of reliability. The analog/digital conversion circuit, constitutedwith a charge/discharge type circuit rather than a sequential comparisoncircuit, assures a high level of anti-noise performance. The structureincludes the circuit that averages a plurality of measurement values,disposed at a stage further rearward relative to the charge/dischargetype analog/digital conversion circuit and thus assures a very robustanti-noise function. While erroneous operation or erroneous measurementtends to occur readily due to significant noise in the inverter in anautomotive power supply system, the structure adopted in the embodimentincludes the circuits described above disposed in each integratedcircuit, enabling the individual integrated circuits to correct theproblems explained earlier independently of one another.

Through the embodiment described below, the following issues areeffectively addressed as well as the issues described earlier.

(Cell Controller)

FIG. 1 shows a battery unit 9 and a cell controller (hereafter may besimply referred to as a C/C) 80 in an automotive battery system used todrive an automotive rotating electrical machine.

The battery unit 9 includes a plurality of battery cell groups GB1, . .. , GBM, . . . and GBN. The battery cell groups each include a pluralityof serially connected battery cells BC1˜BC4. In other words, the batteryunit 9 includes a plurality of serially connected battery cells. Thebattery unit in the embodiment includes numerous battery cells, e.g.,several tens of battery cells or even several hundred battery cells. Thebattery cells in the embodiment are each constituted with a lithium ionbattery.

The terminal voltage at each lithium battery cell changes dependant onthe state of charge at the battery cell. For instance, the terminalvoltage at a given battery cell may be approximately 3.3 V in adischarged state corresponding to an SOC of approximately 30% and it maybe approximately 3.8 V in a charged state corresponding to an SOC ofapproximately 70%. However, in an over-discharged state, in which thebattery cell has been discharged beyond its normal operating range, theterminal voltage may fall to 2.5 V or less, whereas in an over-chargedstate, in which the battery cell has been charged beyond its normaloperating range, the terminal voltage may be 4.2 V or higher. The SOC ofeach of the plurality of serially connected battery cells BC1˜BC4 can beascertained by individually measuring the terminal voltages.

In the embodiment, each battery cell group is constituted with four tosix battery cells BC1˜BC4, so as to facilitate the measurement of theterminal voltages at the individual battery cells BC1˜BC12. In theexample presented in FIG. 1, each battery cell group is made up withfour battery cells. Namely, the group BG1, GBM and GBN are eachconstituted with battery cells BC1˜BC4. While there are battery cellgroups each made up with battery cells are present between the group BG1and the group GBM and between the group GBM and the group GBN, thesebattery cell groups assume structures similar to those of the groupsGB1, . . . , GBM, . . . and GBN and for purposes of simplification, FIG.1 does not include an illustration of the other battery cell groups.

The cell controller 80 includes integrated circuits 3A, . . . , 3M, . .. and 3N, each provided in correspondence to one of the groups GB1, . .. , GBM, . . . and GBN constituting the battery unit 9. The integratedcircuits each include voltage detection terminals via which the terminalvoltages at the individual battery cells are detected. The voltagedetection terminals V1 through GND at each integrated circuit areconnected to the positive poles and the negative poles of the individualbattery cells constituting the corresponding battery cell group. Theintegrated circuit further includes transmission/reception terminalsused for signal transmission. The transmission/reception terminals atthe individual integrated circuits are serially connected as explainedlater and are connected to a battery controller 20 through a signaltransmission path. This structural feature is to be described in detailbelow.

The cell controller 80 includes a plurality of integrated circuits,e.g., several integrated circuits or several tens of integratedcircuits, each provided in correspondence to a specific battery cellgroup. FIG. 1 shows the integrated circuits (hereafter may be simplyreferred to as ICs) 3A, . . . , 3M, . . . and 3N. While integratedcircuits assuming structures similar to those of the integrated circuits3A, 3M and 3N are present between integrated circuits 3A and 3M andbetween the integrated circuits 3M and 3N. For purposes ofsimplification, FIG. 1 does not include an illustration of the otherintegrated circuits.

The integrated circuits 3A, . . . , 3M, . . . and 3N respectively detectthe voltages at the battery cells BC1˜BC4 constituting the correspondingbattery cell groups GB1, . . . , GBM, . . . and GBN. In addition, inorder to achieve uniformity with regard to the states of charge (SOCs)of the battery cells constituting all the battery cell groups, theintegrated circuits 3A, . . . , 3M, . . . and 3N each assume a structurewhereby SOC adjustment resistors R1˜R4 to be used to individually adjustthe SOCs at the battery cells BC1˜BC4 are connected in parallel with thecorresponding battery cells via switch elements. The switch elements areto be described in detail in reference to FIG. 2.

The integrated circuits 3A, . . . , 3M, . . . and 3N have a function ofdetecting an abnormal state occurring at any of the battery cellsBC1˜BC4 constituting the corresponding battery cell groups GB1, . . . ,GBM, . . . and GBN. The integrated circuits adopt structures identicalto one another and each includes (1) a terminal voltage measurementcircuit, (2) an SOC adjustment circuit and (3) an abnormal statedetection circuit, for the corresponding battery cells. The term“abnormal state” is used in the description of the embodiment to referto an over-charge or an over-discharge of a battery cell, an abnormalrise in the battery cell temperature or the like.

Signals are exchanged between the integrated circuits 3A, . . . , 3M, .. . and 3N and the higher-order battery controller 20 through acommunication harness 50. The battery controller 20, grounded (GND) atthe potential assumed at the vehicle chassis, operates at a lowpotential of 12 V or less. The integrated circuits 3A, . . . , 3M, . . .and 3N are held at varying potentials, since the potentials at thebattery cells constituting the corresponding groups are different andthus operate at different potentials. As described earlier, the terminalvoltage at a given battery cell changes based upon its SOC and thus, thepotential at each group relative to the minimum potential of the batteryunit 9 changes in correspondence to the states of charge SOCs. Since theintegrated circuits 3A, . . . , 3M, . . . and 3N each detect theterminal voltages of the battery cells constituting the correspondingbattery cell group in the battery unit 9 or each executes dischargecontrol or the like to adjust the states of charge SOCs at the batterycells constituting the corresponding group, the voltage differenceapplied to the integrated circuit can be reduced by adjusting thereference potential of the integrated circuit based upon the potentialof the corresponding group. A lesser extent of variance among voltagesapplied to the integrated circuits is advantageous in that a very highlevel of voltage withstanding performance does not need to be rigorouslypursued with regard to the integrated circuits and in that better safetyand better reliability are assured. Accordingly, the reference voltagefor each integrated circuit is adjusted based upon the potential at thecorresponding group in the embodiment. By connecting the GND terminalassuming the reference potential for the integrated circuit to a batterycell in the corresponding group, the reference potential of theintegrated circuit can be altered based upon the potential of thecorresponding group. In the embodiment, a terminal of the battery cellassuming the lowest potential in the group is connected to the GNDterminal of the integrated circuit.

In addition, in order to allow each integrated circuit to initiallygenerate a reference voltage and a drive voltage to be used to engagethe internal circuits disposed therein a V1 terminal of the integratedcircuit is connected to a positive-pole terminal of the battery cellassuming the highest potential in the corresponding group and the GNDterminal of the integrated circuit is connected to a negative-poleterminal of the battery cell assuming the lowest potential in the group.The integrated circuits structured as described above is engaged inoperation as a voltage representing the difference between the highestpotential and the lowest potential in the corresponding group issupplied thereto.

The relationship among the potentials manifesting in the power supplysystem for the battery controller 20 and the relationship among thepotentials manifesting in the power supply system for the cellcontroller 80 are different from each other and the values of thevoltages generated therein also differ greatly. Accordingly, thecommunication harness 50 connected to the battery controller 20 needs tobe electrically insulated from transmission paths 52 and 54 throughwhich the transmission/reception terminals of the individual integratedcircuits 3A, . . . , 3M, . . . and 3N are serially connected. Suchelectrical insulation is assured via insulating circuits disposed on theentry sides and the exit sides of the transmission paths 52 and 54constituted with the integrated circuits.

The insulating circuit disposed on the entry side of the transmissionpaths 52 and 54 is indicated as an entry-side interface INT(E), whereasthe insulating circuit disposed on the exit side is indicated as anexit-side interface INT(O). The interfaces INT(E) and INT(O) eachinclude a circuit via which an electrical signal is first converted toan light signal and then the light signal is converted back to anelectrical signal. Information is transmitted via this circuit. As aresult, the electrical circuit of the battery controller 20 and theelectrical circuit of the cell controller 80 remain electricallyinsulated from each other. The entry-side interface INT(E) includesphotocouplers PH 1 and PH2. The photocoupler PH 1 is disposed between atransmission terminal TX of the battery controller 20 and a receptionterminal RX of the integrated circuit 3A on the high potential side. Thephotocoupler PH 2 is disposed between a transmission terminal FF-TEST ofthe battery controller 20 and a reception terminal FFI of the integratedcircuit 3A. Via the photocouplers PH land PH 2 in the entry-sideinterface INT(E), the transmission terminals TX and FF-TEST of thebattery controller 20 remain electrically insulated from the receptionterminals RX and FFI at the integrated circuit 3A and vice versa.

Likewise, photocouplers PH3 and PH4 constituting the exit-side interfaceINT(O) are disposed between reception terminals at the batterycontroller 20 and the low-potential-side integrated circuit 3N, so as tosustain the reception terminals at the battery controller 20 and thetransmission terminals at the integrated circuit 3N in a state ofelectrical insulation from each other. More specifically, thephotocoupler PH 3 is disposed between the transmission terminal TX ofthe integrated circuit 3N and the reception terminal RX of the batterycontroller 20, whereas the photocoupler PH4 is disposed between thetransmission terminal FFO of the integrated circuit 3N and the receptionterminal FF of the battery controller 20.

A signal transmitted from the transmission terminal TX of the batterycontroller 20 travels through the integrated circuits 3A, . . . , 3M, .. . and 3N along the looped communication path and is received at thereception terminal RX. Namely, the signal transmitted from thetransmission terminal TX of the battery controller 20 is received at thereception terminal RX of the integrated circuit 3A via the photocouplerPH 1 in the entry-side interface INT(E), is transmitted from thetransmission terminal TX of the integrated circuit 3A, is received atthe reception terminal RX of the integrated circuit 3M, is transmittedfrom the transmission terminal TX of the integrated circuit 3M, isreceived at the reception terminal RX of the integrated circuit 3N, istransmitted from the transmission terminal TX of the integrated circuit3N and is finally received at the reception terminal RX of the batterycontroller 20 via the photocoupler PH 3 in the exit-side interfaceINT(O). Serial communication is executed via this looped communicationpath. It is to be noted that measurement values indicating the terminalvoltage at each battery cell, the temperature at the battery cell andthe like are received at the battery controller 20 through the serialcommunication. In addition, the integrated circuits 3A through 3N areeach configured so as to automatically enter a wake-up state uponreceiving a command via the transmission path. Namely, as acommunication command 292, to be detailed later, is transmitted from thebattery controller 20, the integrated circuits 3A through 3N each shiftfrom a sleep state into an operating state.

The integrated circuits 3A through 3N each executes an abnormalitydiagnosis and transmits a one-bit signal via the following transmissionpath in the event of an abnormality. The integrated circuits 3A through3N each transmits an abnormality signal from the transmission terminalFFO if it is determined that an abnormality has occurred in theintegrated circuit itself or if a signal indicating an abnormality,transmitted from the preceding integrated circuit is received at thereception terminal FFI. If, on the other hand, a signal indicating anabnormality, which has already been received at the reception terminalFFI, disappears or if an abnormal decision having been made with regardto the subject integrated circuit is switched to a normal decision, theabnormality signal to be transmitted from the transmission terminal FFOdisappears. The abnormality signal used in the embodiment is a one-bitsignal. While the battery controller 20 does not transmit an abnormalitysignal to the integrated circuits, it transmits a test signal, i.e., adummy abnormality signal to be used in diagnosis of the abnormalitysignal transmission path for the correct operating state, from aterminal FF-TEST of the battery controller 20. Next, the transmissionpath is described.

The test signal, i.e., the dummy abnormality signal, is transmitted fromthe transmission terminal FFTEST of the battery controller 20 to thereception terminal FFI of the integrated circuit 3A via the photocouplerPH 2 in the entry-side interface INT(E). In response to the signal, asignal indicating an abnormality (hereafter referred to as anabnormality signal) is transmitted from the transmission terminal FFO ofthe integrated circuit 3A to the reception terminal FFI of the nextintegrated circuit, . . . and is transmitted to the reception terminalFFI of the integrated circuit 3M. The abnormality signal, transmitted insequence as described above, is ultimately transmitted to the receptionterminal FF of the battery controller 20 via the photocoupler PH 4 inthe exit-side interface INT(O) from the transmission terminal FFO ofintegrated circuit 3N. As long as the transmission path is workingnormally, the dummy abnormality signal transmitted from the batterycontroller 20 returns to the reception terminal FF of the batterycontroller 20 via the communication path. The communication pathdiagnosis can be thus executed as the dummy abnormality signal istransmitted and received at the battery controller 20, as describedabove, ensuring an improvement in the system reliability. In addition,as explained earlier, an integrated circuit transmits an abnormalitysignal to the succeeding integrated circuit upon detecting an abnormalstate so as to report the abnormal state quickly to the batterycontroller 20 without requiring the battery controller 20 to issue atransmission request. As a result, the optimal action for correcting theabnormality can be taken promptly.

While the signals are invariably passed on from the integrated circuit3A corresponding to the high potential group in the battery unit 9toward the integrated circuit 3N corresponding to the low potentialgroup in the battery unit 9 in the description provided above, thistransmission sequence simply represents an example. For instance, asignal may instead be transmitted from the battery controller 20 to theintegrated circuit 3N corresponding to the low potential group in thebattery unit 9, then transmitted to the individual integrated circuits(including the integrated circuit 3M) corresponding to higher potentialgroups in sequence and transmitted to the battery controller 20 via theinterface INT from the integrated circuit 3A corresponding to thehighest potential group.

In the DC power supply system shown in FIG. 1, DC power is supplied to aload such as the inverter via a positive pole-side relay RLP and anegative pole-side relay RLN. The battery controller 20 or the inverterexecutes open/close control of the relays RLP and RLN as an abnormalityis detected by an integrated circuit.

The battery controller 20 receives the output from an ammeter Si,detects the electrical current supplied from the overall battery unit 9to the inverter and also detects the DC voltage applied to the inverterfrom the battery unit 9 based upon the output from a voltmeter Vd.

(Integrated Circuits)

FIG. 2 is a block diagram of an electronic circuit representing anexample of the integrated circuit 3A. As explained earlier, theintegrated circuits 3A, . . . , 3M, . . . and 3N adopt structuresidentical to one another. In other words, the integrated circuits otherthan the integrated circuit 3A, too, may assume the structure shown inFIG. 2. The integrated circuit 3A in FIG. 2 is connected to the batterycells BC1˜BC4 in the group GB1 in the battery unit 9 corresponding tothe particular integrated circuit. The integrated circuits other thanthe integrated circuit 3A, too, are connected to the correspondinggroups in the battery unit 9 and are engaged in similar operation. It isto be noted that while the integrated circuit 3A and the resistors R1˜R4are all disposed in the cell controller 80 as shown in FIG. 1, FIG. 2does not include an illustration of the cell controller 80.

Input-side terminals of the integrated circuit 3A are connected to thebattery cells BC1˜BC4 constituting the group GB1. The positive-poleterminal of the battery cell BC1 is connected to a selection circuit 200via the input terminal V1. The selection circuit 200, which may beconstituted with, for instance, a multiplexer, includes switches 120A,120BB, 120C, 120D and 120E. One of the terminals of the switch 120A isconnected to the input terminal V1, whereas the other terminal of theswitch 120A is connected to a power source circuit 121 and a voltagedetection circuit 122 constituted with an analog/digital converter. Thenegative-pole terminal of the battery cell BC1, which is also thepositive-pole terminal of the battery cell B2, is connected to one ofthe terminals of the switch 120B in the selection circuit 120 via theinput terminal V2. The other terminal of the switch 120B is connected tothe voltage detection circuit 122. The negative-pole terminal of thebattery cell BC2, which is also the positive-pole terminal of thebattery cell B3, is connected to one of the terminals of the switch 120Cin the selection circuit 120 via the input terminal V3. The otherterminal of the switch 120C is connected to the voltage detectioncircuit 122. The negative-pole terminal of the battery cell BC3, whichis also the positive-pole terminal of the battery cell BC4, is connectedto one of the terminals of the switch 120D in the selection circuit 120via the input terminal V4. The other terminal of the switch 120D isconnected to the voltage detection circuit 122.

The negative-pole terminal of the battery cell BC4 is connected to theGND terminal at the integrated circuit and is ultimately connected toone of the terminals of the switch 120E in the selection circuit 120 viathe GND terminal. The other terminal of the switch 120E is connected tothe voltage detection circuit 122.

The power source circuit 121, which may be constituted with, forinstance, a DC/DC converter, converts power from the individual batterycells BC1˜BC4 to predetermined constant voltages. These voltages aresupplied to the various circuits within the integrated circuit 3A to beused as drive power or supplied to a comparator circuit where it is usedas a comparison reference voltage when judging the current state.

The voltage detection circuit 122 includes a circuit that converts theterminal voltage at each of the battery cells BC1˜BC4 to a digitalvalue. The terminal voltages having been converted to digital values areprovided to an IC control circuit 123 where they are held in an internalstorage circuit 125. These voltage values are used in the diagnosis andthe like and are also transmitted to the battery controller 20 shown inFIG. 1 from a communication circuit 127.

The IC control circuit 123, equipped with an arithmetic operationfunction, includes the storage circuit 125, a power management circuit124 and a timing control circuit 252 that cyclically detects variousvoltages and executes a state diagnosis. In the storage circuit 125,which may be constituted with, for instance, a register circuit, theterminal voltages at the battery cells BC1˜BC4 detected by the voltagedetection circuit 122 are stored in correspondence to the individualbattery cells BC1˜BC4. In addition, other detection values are held inthe storage circuit 125 at predetermined addresses so that they can beread out as necessary. The power management circuit 124 assumes astructure that enables it to manage the state of the power sourcecircuit 121.

The communication circuit 127 is connected to the IC control circuit 123and thus, the IC control circuit 123 is able to receive a signaloriginating from an external sender outside the integrated circuit 3Avia the communication circuit 127. For instance, the communicationcommand originating from the battery controller 20 can be received atthe RX terminal via the photocoupler PH 1 in the entry-side interfaceINT(E). The communication command is then transferred from thecommunication circuit 127 to the IC control circuit 123, and is decodedat the IC control circuit 125, which then executes processingcorresponding to the contents of the communication command. Such acommunication command may be a communication command requesting themeasurement values indicating the terminal voltages at the battery cellsBC1˜BC4, a communication command requesting a discharge operation to beexecuted in order to adjust the SOCs at the individual battery cellsBC1˜BC4, a communication command (wake-up) for starting operation of theintegrated circuit 3A, a communication command (sleep) for stoppingoperation of the integrated circuit 3A or a communication commandrequesting address setting.

As shown in FIG. 2, the positive-pole terminal of the battery cell BC1is connected to a terminal B1 of the integrated circuit 3A via theresistor R1. A balancing switch 129A is disposed between the terminal B1and the terminal V2. An operating state detection circuit 128A thatdetects the operating state of the balancing switch 129A is connected inparallel to the balancing switch 129A. A discharge control circuit 132executes open/close control for the balancing switch 129A. Likewise, thepositive-pole terminal of the battery cell BC2 is connected to aterminal B2 via the resistor R2 and a balancing switch 129B is disposedbetween the terminal B2 and the terminal V3. An operating statedetection circuit 128B that detects the operating state of the balancingswitch 129B is connected in parallel to the balancing switch 129B. Adischarge control circuit 132 executes open/close control for thebalancing switch 129B.

The positive-pole terminal of the battery cell BC3 is connected to aterminal B3 via the resistor R3 and a balancing switch 129C is disposedbetween the terminal B3 and the terminal V4. An operating statedetection circuit 128C that detects the operating state of the balancingswitch 129C is connected in parallel to the balancing switch 129C. Thedischarge control circuit 132 executes open/close control for thebalancing switch 129C. The positive-pole terminal of the battery cellBC4 is connected to a terminal B4 via the resistor R4 and a balancingswitch 129D is disposed between the terminal B4 and the terminal GND. Anoperating state detection circuit 128D that detects the operating stateof the balancing switch 129D is connected in parallel to the balancingswitch 129D. The discharge control circuit 132 executes open/closecontrol for the balancing switch 129D.

The operating state detection circuits 128A˜128D repeatedly detect thevoltages at the two terminals at the respective balancing switches129A˜129D over predetermined cycles so as to determine whether or notthe balancing switches 129A˜129D are in a normal state. The SOCs of thebattery cells BC1˜BC4 are adjusted via the balancing switches 129A˜129Drespectively. This means that if an abnormality occurs at any of theseswitches, the SOC of the corresponding battery cell cannot becontrolled, giving rise to an over-charge or an over-discharged state inthe particular battery cell. Any one of the balancing switches 129A˜129Dmay be detected to be in an abnormal state if, for instance, the voltagebetween the terminals at the balancing switch, which should be in acontinuous state, matches the terminal voltage at the correspondingbattery cell. Under such circumstances, the balancing switch has failedto enter the continuous state in response to a control signal. Also, ifthe voltage between the terminals at a given balancing switch, whichshould be in an open state, indicates a value lower than that of theterminal voltage at the corresponding battery cell, the particularbalancing switch can be assumed to be continuous regardless of thecontrol signal. The switch operating state detection circuits 128A˜128Dmay be voltage detection circuits each constituted with a differentialamplifier or the like. The terminal voltages are compared with apredetermined voltage used for purposes of making the decision describedabove at an abnormality decision-making circuit 131 to be detailedlater.

Via the balancing switches 129A˜129D, which may each be constitutedwith, for instance, a MOSFET, the power having accumulated in thecorresponding battery cells BC1˜BC4 is discharged. An electrical loadsuch as an inverter is connected to the battery unit 9 constituted withnumerous serially connected battery cells and an electrical current issupplied to the electrical load from the entire assembly of seriallyconnected battery cells. In addition, the battery unit 9 is charged withan electrical current supplied from the electrical load to all thebattery cells connected in series. If the serially connected batterycells assume varying states of charge (SOCs), the current supplied tothe electrical load is regulated in correspondence to the state of thebattery cell at the most advanced stage of discharge among the batterycells. The current supplied from the electrical load, on the other hand,is regulated in correspondence to the state of the battery cell at themost advanced stage of charge among the battery cells.

The balancing switch 129 connected to any battery cell assuming an SOCexceeding the average state among the numerous serially connectedbattery cells is set in a continuous state so as to supply a dischargecurrent via the serially connected registers. As a result, the states ofcharge of the serially connected battery cells are controlled towardequalization. An alternative method whereby the battery cell in the mostadvanced stage of discharge is assigned as a reference cell and thedischarge time for a given battery cell is determined based upon thedifference relative to the SOC of the reference cell may be adopted.There are various other methods that may be adopted for SOC adjustment.The SOC of each battery cell can be determined through arithmeticoperation executed based upon the terminal voltage at the battery cell.There is a correlation between the SOC of the battery cell and theterminal voltage at the battery cell and, accordingly, by controllingthe balancing switches 129 so as to equalize the terminal voltages atthe battery cells, the SOCs of the battery cells can be substantiallyequalized.

The voltage between the source and the drain at the FET constitutingeach balancing switch, detected via the corresponding operating statedetection circuit among the operating state detection circuits128A˜128D, is output to a potential conversion circuit 130. Differentpotentials are set between the sources and the drains at the individualFETs relative to the reference potential at the integrated circuit 3A,and for this reason, accurate judgment cannot be made by comparing theinitial voltage values. Accordingly, the potentials are adjusted at thepotential conversion circuit 130 before undergoing abnormalitydecision-making at the abnormality decision-making circuit 131. Thepotential conversion circuit 130 also has a function of selecting thediagnosis target balancing switch 129 based upon a control signalprovided from the IC control circuit 123. The voltage at the selectedbalancing switch 129 is provided to the abnormality decision-makingcircuit 131. Based upon a control signal provided from the IC controlcircuit 123, the abnormality decision-making circuit 131 compares thevoltage measured between the terminals at the diagnosis target balancingswitch 129, indicated in the signal from the potential conversioncircuit 130, with a decision-making voltage and makes a decision as towhether or not an abnormality has occurred at the target balancingswitch among the balancing switches 129A1˜129D.

A command signal for setting the balancing switch 129, corresponding tothe battery cell to be discharged, in a continuous state is transmittedfrom the IC control circuit 123 to the discharge control circuit 132.Based upon this command signal, the discharge control circuit 132outputs a signal equivalent to a gate voltage at which the balancingswitches 129A˜129D constituted with MOSFETs as explained earlier, enterthe continuous state. The IC control circuit 123, upon receiving throughcommunication a discharge time command indicating the discharge timecorresponding to the specific battery cell from the battery controller20 in FIG. 1, executes the discharge operation described above.

The abnormality decision-making circuit 131 detects whether or not anabnormality has occurred at any of the balancing switches 129A˜129D.

The IC control circuit 123 outputs an abnormality signal indicating thatan abnormality has occurred at any of the balancing switches 129A˜129Dfrom the one-bit transmission terminal FFO of the communication circuit127 and the abnormality signal is subsequently transmitted to thebattery controller 20 via the communication circuits 127 at the otherintegrated circuits. In addition, the IC control circuit 123 transmitsinformation indicating that an abnormality has occurred at a balancingswitch among the balancing switches 129A˜129D and information enablingidentification of the abnormal balancing switch to the batterycontroller 20 via the transmission terminal TX at the communicationcircuit 127.

(Communication Means)

FIG. 3 illustrates a method that may be adopted to transmit and receivecommunication commands at the individual integrated circuits 3A, . . . ,3M, . . . and 3N. FIG. 3( a) shows a signal 3A-RX received at theterminal RX of the integrated circuit 3A, a signal 3A-TX transmittedfrom the terminal TX of the integrated circuit 3A, a signal 3B-RXreceived at the terminal RX of the succeeding integrated circuit 3B, asignal 3B-TX transmitted from the terminal TX of the integrated circuit3B, a signal 3C-RX received at the terminal RX of the succeedingintegrated circuit 3C and a signal 3C-TX transmitted from the terminalTX of the integrated circuit 3C.

The signal 3A-TX transmitted from the terminal TX of the integratedcircuit 3A is split between a resistor RA within the integrated circuit3A and a resistor RB within the integrated circuit 3B, and thus thesignal 3B-RX is generated. The signal 3B-TX transmitted from theterminal TX of the integrated circuit 3B is split between a resistor RB′within the integrated circuit 3B and a resistor RC within the integratedcircuit 3C, and thus the signal 3C-RX is generated. The subsequenttransmission signals are likewise each split via the individualresistors within the integrated circuits connected in series along thecommunication path, thereby determining the potential of thecorresponding reception signal.

FIG. 3( b) indicates the potential levels of the signals 3A-RX, 3A-TX,3B-RX, 3B-TX, 3C-RX and 3C-TX.

As indicated in the figure, in a downstream-side group the voltagethreshold value is set to a level matching half the total of the sum ofvoltages at the four battery cells and the sum of voltages at the twobattery cells. If the signal from the terminal TX of the integratedcircuit 3A is judged with a threshold value similar to that of theintegrated circuit 3A in reference to voltages at battery cellscontrolled by the integrated circuit 3B, the low level of the signalwill equal the half of the total voltage at the integrated circuit 3B,which is bound to lead to problems. Such problematic situation can beavoided by setting the threshold values as described above. It is to benoted that while the explanation is given above by assuming that thesignals are transmitted from the higher potential-side toward the lowerpotential-side, signals may instead be transmitted from the lowerpotential-side toward the higher potential-side by shifting the signallevels through splitting via resistors in a similar manner.

(Diagnosis and Management: (1) Overview of Operation Schedule)

FIG. 4 illustrates the timing with which the measurement operation isexecuted. The integrated circuit 3A in FIG. 2 has a function ofexecuting a diagnosis operation together with a measurement operation.It repeatedly executes measurement with the operational timing shown inFIG. 4 and also executes the diagnosis synchronously with themeasurement. It is to be noted that while the groups GB1˜GBNconstituting the battery unit 9 each include four battery cells in theembodiment illustrated in FIGS. 1 and 2, the integrated circuits 3A˜3Nare each capable of handling up to six battery cells. In other words,the number of battery cells in each of the groups GB1˜GBN can beincreased up to six. Accordingly, the timing diagram presented in FIG. 4indicates the timing with which the operation is executed in conjunctionwith six battery cells. It is to be noted that the specific number ofbattery cells to constitute each group should be determined based uponthe overall number of battery cells, the processing speed with which themeasurement and the diagnosis are executed and the like.

As explained above, FIG. 4 illustrates the timing with which thediagnosis operation and the measurement operation are executed. Thetiming of the measurement operation, the measurement cycles and thediagnosis operation are managed by a startup circuit 254 and a stagecounter unit constituted with a first stage counter 256 and a secondstage counter 258. The stage counters 256 and 258 generate controlsignals (timing signals) to be used to manage the overall operation ofthe integrated circuit 3A. While the stage counters 256 and 258 are notseparate entities in reality, they are shown as separate counters in thefigure for ease of comprehension. The stage counter unit may be astandard counter or it may be constituted with a shift register. If thestage counter unit is constituted with shift registers, the number ofstages at which individual shift registers are disposed matches thenumber of stages. In the embodiment, there are 10 stages.

Upon (1) receiving at the terminal RX a communication command indicatinga wake-up request, transmitted through the transmission path, (2)reaching a predetermined voltage as a power source voltage from the ICpower source in the integrated circuit is supplied thereto or (3)receiving a signal indicating that the vehicle starter switch (keyswitch) has been turned on, the startup circuit 254 outputs a resetsignal to the first and second stage counters 256 and 258, therebyinitializing the stage counters 256 and 258. The startup circuit alsooutputs a clock signal with a predetermined frequency. Namely, under theconditions described in any of (1)˜(3) above, the integrated circuit 3Aexecutes the measurement operation and the diagnosis operation. If, onthe other hand, a communication command indicating a sleep request isreceived through the transmission path or the communication command isnot received over a predetermined length of time or more, the startupcircuit 254 stops outputting the clock with the timing with which thestage counters 256 and 258 resume the reset state, i.e., the initialstate. As the clock output stops, the stage progress also stops andthus, the execution of the measurement operation and the diagnosisoperation enters the stopped state.

Upon receiving the clock signal provided from the startup circuit 254,the first stage counter 256 outputs a count value to be used to controlthe processing timing with which the processing is executed within eachstage. A decoder 257 generates a timing signal STG1 to be used tocontrol the processing timing with which the processing is executedwithin the stage based upon the count value provided from the firststage counter 256. The count value at the second stage counter 258corresponds to the type of each specific stage indicated in a row 260Y1of an operation table 260 and as the count value progresses, thecorresponding stage is switched from the left-hand side stage to theright-hand side stage in row 260Y1 in the operation table 260. A decoder259 outputs a stage signal STG2 to be used to select a specific stagebased upon the count value at the second stage counter 258.

In the reset state, i.e., when the first stage counter 256 and thesecond stage counter 258 are in the initialized state, the second stagecounter 258 holds the count value to be used to identify a stage STGCal,the stage signal STG2 output from the decoder 259 is a signal forselecting the stage STGCal and the processing within the stage isexecuted based upon the count operation at the first stage counter 256.As the count value at the second stage counter 258 is incremented byone, the second stage counter 258 assumes a count value indicating astage STGCV1 in the second position from the left end in row 260Y1 inthe operation table 260. The stage signal STG2 output from the decoder259 at this time indicates STGCV1. At the stage STGCV1, the measurementand the diagnosis are executed for the battery cell BC1. Likewise, asthe count value at the second stage counter 258 goes up, thecorresponding stage indicated in row 260Y1 in the operation table 260 isswitched from the left-hand side to the right-hand side. At the stageSTGCV1, the measurement and the diagnosis are executed for the batterycell BC1. At the next stage STGCV2, the measurement and the diagnosisare executed for the battery cell BC2. At the next stage STGCV3, themeasurement and the diagnosis are executed for the battery cell BC3. Atthe next stage STGCV4, the measurement and the diagnosis are executedfor the battery cell BC4. In the embodiment illustrated in FIG. 2, thegroups GB1˜GBN constituting the battery unit 9 are each made up withfour battery cells and accordingly, stages STGCV5 and STGCV6 may eitherremain unused or be skipped. In other words, the presence of the stagesSTGCV5 and STGCV6 is not relevant. This operation is to be described indetail later. Consequently, following the processing at the stageSTGCV4, processing is executed at a stage STGVDD to measure and diagnosethe output from the power circuit 121 within the integrated circuit.Subsequently, processing is executed at a stage STGTEM to measure anddiagnose the output from a temperature sensor. The processing thenshifts to a stage STG reference power to measure and diagnose thereference voltage used within the integrated circuit. Following theprocessing at the stage STG reference power, the count value at thesecond stage counter 258 resumes the initial value corresponding to thestage STGCal. Thus, the output signal STG2 output from the decoder 259at this time is the signal for specifying the stage STGCal. As describedabove, based upon the count operation at the second stage counter 258,the processing at each of the stages listed in row 260Y1 in theoperation table 260 is executed from left to right repeatedly. It is tobe noted that if a specific value is forcibly set at the second stagecounter 258, the processing is executed at the stage corresponding tothe specific value. The contents of the processing executed within eachstage are to be described in detail later.

(Diagnosis and Measurement: (2) Switching the Number of Battery Cells)

As explained above, the contents of the diagnosis operation and themeasurement operation to be executed are selected depending upon whetherthe number of battery cells constituting individual groups eachcorresponding to a specific integrated circuit is four or six. Aspecific example of the circuit is shown in FIG. 5. Based upon the clocksignal provided from the startup circuit 254, the first stage counter256 repeatedly executes count operation and as the count value at thefirst stage counter 256 becomes equal to a predetermined value, thecount value at the second stage counter 258 is incremented by one.

The second stage counter 258 in the example presented in FIG. 5, is madeup with 10 registers. In the initial state, a shift circuit 1 aloneassumes a state 1 and all other shift circuits 2˜10 assume a state 0.The decoder 259 outputs the stage signal STGCal as its output STG2. Asthe count value at the first stage counter 256 reaches a predeterminedvalue, the next shift circuit 1 shifts into state 1 and the shiftcircuit 1 and the shift circuits 3˜10 all assume state 0. The differentshift circuits assume state 1 in sequence as described above. As theshift circuit 5 assumes state 1 and the shift circuits 1˜4 and 6˜10assume state 0, the decoder 259 outputs the stage signal STGCV4.

When there are six battery cells constituting the corresponding batterycell group, 6 is set at a register 2582 in response to a communicationcommand 292 provided from the outside. If, on the other hand, thecorresponding battery cell group is constituted with four battery cells,4 is set as the number of battery cells at the register 2582 in responseto the communication command 292. When 6 is set at the register 2582 asthe number of battery cells, the stage signal STGCV4 is output from thedecoder 259 as the shift circuit 5 shifts to state 1. Subsequently, theshift circuit 6 shifts into state 1 and the stage signal STGCV5 isoutput. Then, the shift circuit 7 shifts into state 1 and the stagesignal STGCV6 is output. After the shift circuit 7 assumes state 1 theshift circuit 8 shifts to state 1 and the decoder 259 outputs the stagesignal STGVDD.

When 4 is set at the register 2582 as the number of battery cells, theshift circuits 6 and 7 are skipped and the shift circuit 8 assumes state1 after the shift circuit 5, based upon the operation executed at alogic circuit 2584 and a logic circuit 2586. As a result, the stagesignal STGCV5 and the stage signal STGCV6 corresponding to the shiftcircuits 6 and 7 are not output from the decoder 259 and instead, thedecoder 259 outputs the stage signal STGVDD after outputting the stagesignal STGCV4.

While the explanation given above is simplified by focusing on theoperations executed when the number of battery cells constituting eachbattery cell group is four and six, logic circuits fulfilling functionsidentical to those of the logic circuits 2584 and 2586 are disposedbetween other shift circuits as well so as to output stage signalscorresponding to the number of battery cells set at the register 2582among the stage signals STGCV1˜STGCVG and skip any superfluous stagesignals.

At the integrated circuits 3A˜3N disposed in correspondence to thespecific groups GB1˜GBN, as shown in FIG. 1, the numbers of batterycells constituting the corresponding groups GB1˜GBN are set. As aresult, each of the integrated circuits 3A˜3N is able to generate stagesignals corresponding to the number of battery cells constituting thespecific battery cell. This structure allows the groups GB1˜GBN to beconstituted with varying numbers of battery cells, which, in turn,increases the level of freedom in design and enables high-speedprocessing.

(Diagnosis and Measurement: (3) Measurement of Terminal Voltage at EachBattery Cell and Diagnosis for the Battery Cell)

Next, in reference to FIG. 4, details of the measurement and thediagnosis executed at each of the stages listed in row 260Y1 of theoperation table 260 are explained. The measurement/diagnosis iscategorized into two primary types. In one type ofmeasurement/diagnosis, the measurement is executed by sensors and thediagnosis is executed to determine whether or not the measurement targetis in an abnormal state. Its measurement schedule is indicated in a row260Y2. In the other type of measurement/diagnosis, self-diagnosis isexecuted for the control device including the integrated circuit, i.e.,self-diagnosis for the measurement system or the battery cell dischargecontrol system shown in FIG. 2. Although not shown in FIG. 4, theoperation table 260 should further include rows 260Y3˜260Y9, wheredetails of the self-diagnosis at the measurement system and thedischarge control system would be indicated, below row 260Y2. Asindicated in row 260Y2, each measurement operation session is dividedinto two time segments. The first half of the measurement session isindicated as RES, whereas the second half of the measurement session isindicated as “measurement”. During the first time segment RES of eachstage, an analog/digital converter 122A to be used for the measurementis initialized in addition to executing the diagnosis corresponding tothe particular stage. In the embodiment, the analog/digital converter122A adopting a charge/discharge method in conjunction with a capacitoris used so as to lessen the adverse effect of noise. The electricalcharge having been accumulated at the capacitor during the previousoperation is discharged with the timing of the first time segment RES.During the second time segment “measurement” at each of the stageslisted in row 260Y2, measurement is executed via the analog/digitalconverter 122A and diagnosis is executed for the measurement targetbased upon the measured value.

At the stage STGCal, the self-diagnosis, the details of which would beset in rows 260Y3˜260Y9 (not shown) is primarily executed. In the RESmode during the first time segment at the stage STGCal, self-diagnosisis executed for the selection circuit 120 (multiplexer) as set in row260Y6 (not shown), diagnosis is executed for a switching circuit thatexecutes a switching operation for the selection circuit 120 and thelike as set in row 260Y7 (not shown), and diagnosis of a selectionsignal (a selection signal used at a current value storage circuit 274or a reference value storage circuit 278 in FIG. 6 to be detailed later)used in the digital comparison operation within the integrated circuitis executed as set in row 260Y9 (not shown). During the second timesegment “measurement” at the stage STGCal, “measurement of the terminalvoltage at the balancing switch 129 used to adjust the SOC of a specificbattery cell” and “diagnosis for the balancing switch 129” are executedas set in row 260Y3 (not shown) and also, “diagnosis for the digitalcomparator circuit within the integrated circuit” is executed as set inrow 260Y5 (not shown). The individual diagnosis sessions set in row260Y7 (not shown) and the sessions set in row 260Y9 (not shown) are allexecuted during the first time segment and the second time segment atall the stages. However, this diagnosis cycle simply represents anexample and the diagnosis may be executed over longer intervals insteadof at each stage. In the diagnosis set in row 260Y8 (not shown),diagnosis is executed to determine whether or not the circuit thatgenerates a threshold value to be used to detect an over-charged stateof a battery cell is in the normal state. If an abnormality occurs atthe threshold value generating circuit, accurate over-charge diagnosiscannot be executed.

At the stages STGCV1˜STGCV6, the voltages at the terminals of thebattery cells are measured in sequence and the diagnosis is executedbased upon the values obtained through the measurement as to whether anyof the battery cells may be at risk of over-charge or over-discharge.Since it is dangerous to allow the battery cells to enter anover-charged state or an over-discharged state, theover-charge/over-discharge diagnosis is executed with safety margins.When the subject battery cell group is made up with four battery cells,as shown in FIGS. 1 and 2, the stages STGCV5 and STGCV6 are skipped, ashas been explained in reference to FIG. 5. At the stage STGVDD, theoutput voltage from the power circuit 121 is measured, whereas at thestage STGTEM, the voltage output at the thermometer is measured. At thestage STGTEM, the diagnosis session set in a row 260Y4 (not shown),i.e., the diagnosis as to whether or not the analog circuits and theanalog/digital converter within the integrated circuit and thereferenced voltage generating circuit are together operating in a normalstate, is executed. The voltage output from the referenced voltagegenerating circuit assumes a known voltage value, and if the results ofvoltage value measurement do not indicate a value within a predeterminedrange, it is determined that an abnormality has occurred at one of thecircuits listed above. Under such circumstances, execution of control isjudged to be dangerous.

(Diagnosis and Measurement: (4) Measurement Circuit and DiagnosisCircuit)

FIG. 6 shows the measurement circuit and the diagnosis circuit. Theselection circuit 120 functions as a multiplexer. The measurementoperation executed in the integrated circuit 3A to measure the terminalvoltages at the individual battery cells in the group GB1 in the batteryunit 9 is first described. Based upon the stage signal STGCV1 havingbeen explained in reference to FIG. 4, the selection circuit 120 selectsthe terminals V1 and V2. As a result, the terminal voltage at thebattery cell BC1 shown in FIGS. 1 and 2 is output to the voltagedetection circuit 122 via the selection circuit 120.

The voltage detection circuit 122 includes a differential amplifier 262and the analog/digital converter 122A. The differential amplifier 262 isconstituted with an operational amplifier 1220P and resistors122R1˜122R4. The differential amplifier 262 has a function of adjustingpotentials different from one another, i.e., a level shift function, andgenerates an analog output based upon the difference among the voltagesat input terminals regardless of the variance in the potentials at theindividual input terminals. Consequently, the influence of the potentialdifferences manifesting at the serially connected battery cells relativeto the reference potential is eliminated and an output is generatedbased upon the terminal voltage at the battery cell BC1. The output fromthe differential amplifier 262 is digitized by the analog/digitalconverter 122A and the digitized output is then input to an averagingcircuit 264. The averaging circuit 264 determines the average value ofthe values indicated in the results of a predetermined number ofmeasurements. Assuming that the average value has been determined incorrespondence to the battery cell BC1, it is held at BC1 in the currentvalue storage circuit 274. The averaging circuit 264 calculates theaverage value of the values obtained through a predetermined number ofmeasurements indicated at an averaging control circuit 263 and theaverage value output from the averaging circuit is held at the currentvalue storage circuit 274 mentioned earlier. If the averaging controlcircuit 263 indicates 1, the output from the analog/digital converter122A is directly held at BC1 in the current value storage circuit 274without undergoing averaging operation. If, on the other hand, theaveraging control circuit 263 indicates 4, the values indicated in theresults of the four measurements of the terminal voltage at the batterycell BC1 are averaged and the average value is held at BC1 in thecurrent value storage circuit 274. While four measurements need to beexecuted initially at the corresponding stages shown in FIG. 4 in orderto calculate the average value of the four measurement values, theaveraging operation at the averaging circuit 264 can be subsequentlyexecuted following each measurement session by using the fourmeasurement values indicated in the most recent measurement results. Asexplained earlier, the adverse effect of noise can be eliminated via theaveraging circuit 264, which calculates the average value of apredetermined number of measurement values. The DC power from thebattery unit 9 shown in FIG. 1 is supplied to the inverter where it isconverted to AC power. As the DC power is converted to AC power at theinverter, current on/off operation is executed at high speed, generatingsignificant noise. The adverse effect of such noise can be reduced bythe averaging circuit 264.

The digital value indicating the terminal voltage at the battery cellBC1, resulting from the digital conversion, is held at the register BC1in the current value storage circuit 274. The measurement operationdescribed above is executed within the period of time indicated as“measurement” at the stage STGCV1 in FIG. 4. In addition, the diagnosisoperation is executed successively during the time period indicated as“measurement” at the stage STGCV1. During the diagnosis operation,over-charge diagnosis and over-discharge diagnosis are executed. Thedigital value indicating the terminal voltage at the battery cell BC1 isheld at the register BC1 in the current value storage circuit 274. Then,based upon the stage signals STG2 and STG1, a digital multiplexer 272reads out the terminal voltage at the battery cell BC1 from the registerBC1 in the current value storage circuit 274 and transmits it to adigital comparator 270. In addition, a digital multiplexer 276 reads outan over-charge decision-making reference value OC from the referencevalue storage circuit 278 and transmits it to the digital comparator270. The digital comparator 270 compares the terminal voltage at thebattery cell BC1 having been read from the register BC1 with theover-charge decision-making reference value OC and if the terminalvoltage at the battery cell BC1 is greater than the over-chargedecision-making reference value OC, it sets a flag (diagnosis flag)indicating an abnormality at a flag storage circuit 284. It also sets aflag (OC flag). Occurrence of an actual over-charged state is rare sincecontrol is executed so as to prevent such an eventuality. However, thediagnosis is executed repeatedly in order to guarantee a required levelof reliability.

Following the over-charge diagnosis, the over-discharge diagnosis isexecuted. The digital multiplexer 272 reads out the terminal voltage atthe battery cell BC1 from the register BC1 in the current value storagecircuit 274 and transmits it to the digital comparator 270. In addition,the digital multiplexer 276 reads out an over-discharge decision-makingreference value OD from the reference value storage circuit 278 andtransmits it to the digital comparator 270. The digital comparator 270compares the terminal voltage at the battery cell BC1 having been readfrom the register BC1 with the over-discharge decision-making referencevalue OD and if the terminal voltage at the battery cell BC1 is lessthan the over-discharge decision-making reference value OD, it sets aflag (diagnosis flag) indicating an abnormality at the flag storagecircuit 284 and also sets a flag (OC flag). As in the case ofover-charge diagnosis, the control is executed so as to preempt asituation in which an over-discharged state actually occurs, such anover-discharge hardly ever manifests. However, the diagnosis is executedrepeatedly in order to guarantee a required level of reliability

The explanation provided above relates to the measurement and thediagnosis executed for the battery cell BC1 at the stage STGCV1 in FIG.4. Likewise, the selection circuit 120 in FIG. 6 selects the terminalvoltage at the battery cell BC2 and outputs the selected terminalvoltage to the voltage detection circuit 122 at the next stage STGCV2.The terminal voltage is digitized at the voltage detection circuit 122,the average value is calculated at the averaging circuit 264 and theaverage value is held at the register BC2 in the current value storagecircuit 274. The terminal voltage at the battery cell B2 read out fromthe register BC2 by the digital multiplexer 272 is then compared withthe over-charge decision-making reference value OC and also the terminalvoltage at the battery cell B2 is compared with the over-dischargedecision-making reference value OD. An abnormal state is judged throughthe comparison of the terminal voltage with the over-chargedecision-making reference value OC and the comparison of the terminalvoltage with the over-discharge decision-making reference value OD. Ifit is judged to be an abnormal state, a flag (diagnosis flag) indicatingan abnormality is set ( ) and a flag (OC flag) or a flag (OD flag)indicating the cause of the abnormality is also set in the flag storagecircuit 284.

Subsequently, the terminal voltage at the battery cell BC3 is measuredand the over-charge/over-discharge diagnosis is executed for the batterycell BC3 at the stage STGCV3 in FIG. 4 and the terminal voltage at thebattery cell BC4 is measured and the over-charge/over-dischargediagnosis is executed for the battery cell BC4 at the stage STGCV4 inFIG. 4,

(Diagnosis and Measurement: (5) Measurement of Battery Cell TerminalVoltages and Holding of Initial Data)

In the DC power supply system shown in FIG. 1, no current is suppliedfrom the battery unit 9 to the inverter in a vehicle stopped statebefore the driver starts driving the vehicle. Based upon the terminalvoltages at the individual battery cells measured while nocharge/discharge currents are flowing through the battery cells, thestates of charge (SOCs) of the battery cells can be determinedaccurately. Accordingly, in response to a vehicle key switch operationor a communication command 292 such as a wake-up request issued from thebattery controller 20, the integrated circuits in the embodiment eachautomatically start measurement operation. At each integrated circuit,the measurement operation and the battery cell diagnosis operationstart, as has been described in reference to FIG. 6. Once themeasurement has been executed the number of times held in the averagingcontrol circuit 263, the averaging circuit 264 executes arithmeticoperation to calculate the average measurement value. The results of thearithmetic operation are held in the current value storage circuit 274.The integrated circuit executes the measurement operation and themeasurement result averaging operation for all the battery cells in thecorresponding group independently of the other integrated circuits. Thearithmetic operation results are held at the registers BC1˜BC6 in thecurrent value storage circuit 274 of the particular integrated circuit.

It is desirable to measure the terminal voltages at the individualbattery cells while no charge/discharge currents flow through thebattery cells, in order to ensure that the state of charge (SOC) at eachbattery cell is subsequently ascertained accurately. As described above,each integrated circuit starts the measurement operation on its own soas to measure the terminal voltages at all the battery cellscorresponding to the particular integrated circuit before the currentsupply from the battery unit 9 to the inverter starts and these terminalvoltage measurement values are held at the registers BC1˜BC6 in thecurrent value storage circuit 274. Since each measurement value held atthe current value storage circuit 274 is subsequently overwritten with avalue indicating new measurement results, the measurement resultsobtained prior to the current supply start are transferred from theregisters BC1˜BC6 in the current value storage circuit 274 to registersBBC1˜BBC6 in the initial value storage circuit 275 to be held therein.Since the measurement values obtained before starting the current supplyfrom the battery unit 9 to the inverter are held at the initial valuestorage device 275 as described above, high priority diagnosisprocessing can be executed ahead by relegating processing such ascalculation of the SOCs to a later step. Once the high priorityprocessing is executed and the current supply from the battery unit 9 tothe inverter starts, the SOCs of the individual battery cells aredetermined through arithmetic calculation based upon the measurementvalues held in the initial value storage circuit 275, enabling controlfor adjusting the states of charge (SOCS) to be executed based uponaccurate state detection. The driver of the vehicle may wish to startdriving immediately and, for this reason, it is desirable to immediatelystart the current supply to the inverter as explained above.

In the embodiment described in reference to FIG. 6, as the measurementvalues obtained prior to starting the current supply to the electricalload, i.e., the inverter, become held at the current value storagecircuit 274, the digital comparator circuit 270 is allowed to executethe over-charge/over-discharge diagnosis and also diagnosis for currentleakage or the like. This means that an abnormal state can be detectedeven before starting the DC power supply to the inverter. If an abnormalstate exists, the abnormality can be detected through the diagnosisexecuted prior to the current supply start, allowing appropriate actionsuch as refraining from supplying DC power to the inverter, to betaken.In addition, the measurement values obtained prior to the current supplystart are transferred from the current value storage circuit 274 to theinitial value storage circuit 275, which is used as a dedicated storagecircuit for holding the preliminary measurement values. In short, theoperation executed as described above is markedly advantageous in thatbetter safety is assured and that the states of charge (SOCs) can beascertained with better accuracy.

(Communication Commands)

The communication circuit 127 via which communication commands aretransmitted/received is installed within the integrated circuit 3A shownin FIG. 2. FIG. 7 is a circuit diagram showing the circuit structure andthe operation of the communication circuit 127. As explained earlier,the other integrated circuits assume structures identical to that of theintegrated circuit 3A and execute operations identical to that executedin the integrated circuit 3A. Accordingly, the operation of thecommunication circuit 127 is described by referring to the circuitstructure assumed in the integrated circuit 3A representing the otherintegrated circuits as well. A communication command transmitted fromthe battery controller 20 and received at a reception terminal RX of thecommunication circuit 127 is constituted with a total of five datasegments each corresponding to an 8-bit unit and its basic structureincludes five bytes. However, a communication command may sometimes belonger than five bytes, as explained later, and accordingly, the lengthof communication commands is not limited to five bytes. Thecommunication command is input to a reception register 322 from theterminal RX and is held at the communication register 322. It is to benoted that the reception register 322 is a shift register at whichsignals input serially from the terminal RX are shifted in sequence inthe order with which the signals are input to the reception register322. The leading segment of the communication command is held as a breakfield segment 324 at the leading segment of the register and thesubsequent segments of the communication command are held in sequence.

The communication command 292 held at the reception register 322 assumesthe following structure. The leading eight bits constitute the breakfield 324 made up with a signal indicating a signal arrival and thesecond eight bits constitute a synchronous field 326 made up with asynchronizing signal. The third eight bits constitute an identifier 328indicating a specific integrated circuit among the integrated circuits3A, . . . , 3M, . . . and 3N, the target address, which indicates thelocation of the instruction target circuit and the contents of thecommand. The fourth eight bits are data 330 indicating the communicationcontents (control contents), which are needed in the execution of theinstruction. This segment may contain data other than one-byte data. Thefifth eight bits constitute a checksum 332 used to check whether or notthere has been any error in the transmission/reception operation withwhich a failure to communicate the command accurately due to noise orthe like can be detected. As described above, the communication commandsoriginating from the battery controller 20 is constituted of fivesegments, i.e., the break field 324, the synchronous field 326, theidentifier 328, the data 330 and the checksum 312. Assuming each segmentis constituted with a single byte of data, the overall communicationcommand is constituted with five bytes. While communication commandsbasically adopt this five-byte structure, the length of the data 330 maybe other than one byte. In other words, the length may be increased asnecessary.

The synchronous field 326 is used to synchronize a transmission clock onthe transmission side and a reception clock on the reception side. Asynchronous circuit 342 detects the timing with which the individualpulses of the synchronous field 326 are transmitted and synchronizesitself with the timing with which each pulse of the synchronous field326 is transmitted. The reception register 322 receives at thesubsequent signals with the synchronized timing. Through these measures,the optimal timing with which a received signal is compared with thethreshold value used to judge the true value of the signal can beselected accurately so as to minimize the risk of erroneoustransmission/reception.

As shown in FIG. 1, the communication command 292 is transmitted fromthe battery controller 20 to the terminal RX of the integrated circuit3A, is transmitted from the terminal TX of the integrated circuit 3A tothe terminal RX of the succeeding integrated circuit, . . . , istransmitted to the terminal RX of the succeeding integrated circuit 3M,is transmitted from the terminal TX of the integrated circuit 3M to theterminal RX of the succeeding integrated circuit, . . . , is transmittedto the terminal RX of the succeeding integrated circuit 3N and istransmitted from the terminal TX of the integrated circuit 3N to theterminal RX of the battery controller 20. In short, the communicationcommand 292 is communicated through a transmission path 52 constitutedby serially connecting the transmission/reception terminals of theindividual integrated circuits in a loop.

While the integrated circuit 3A is described as a representative exampleof all the integrated circuits, and the other integrated circuits assumestructures and execute operations identical to those of the integratedcircuit 3A. The communication command 292 is transmitted to the terminalRX of the integrated circuit 3A and at each subsequent integratedcircuit, the communication command 292 is transmitted from the terminalTX thereof to the next integrated circuit. During this operation, acommand processing circuit 344 shown in FIG. 7 makes a decision as towhether or not the instruction target of the communication command 292having been received is the subject integrated circuit. If the subjectintegrated circuit is judged to be the instruction target, processing isexecuted based upon the communication command. The procedure describedabove is executed at the individual integrated circuits in sequence asthe communication command 292 is transmitted and received.

Accordingly, even when the communication command 292 held at thereception register 322 does not concern the integrated circuit 3A, thecommunication command 292 having been received must be passed on to thesucceeding integrated circuit. The contents of the identifier 328 in thereceived communication command 292 are taken into the command processingcircuit 344 and, based upon the identifier thus taken in, the commandprocessing circuit makes a decision as to whether or not the subjectintegrated circuit 3A itself is the target of the communication command292. If it is decided that the integrated circuit 3A is not the targetof the communication command 292, the contents of the identifier 328 andthe data 330 are directly transferred into portions of a transmissionregister 302 designated as an identifier 308 and data 310 respectively.In addition, a transmission signal is generated within the transmissionregister 302 by inputting the checksum 312 used to check for anyerroneous transmission/reception operation and the transmission signalthus generated is transmitted from the terminal TX. As is the receptionregister 322, the transmission register 302 is constituted with a shiftregister.

If the target of the received communication command 292 is the subjectintegrated circuit itself, the instruction is executed based upon thecommunication command 292. The command execution is described below.

The target of the received communication command 292 may be all theintegrated circuits including the subject integrated circuit. Such acommunication command may be, for instance, an RES command, awake-upcommand or a sleep command. Upon receiving the RES command, the commandprocessing circuit 344 decodes the contents of the command and outputsan RES signal. As the RES signal is generated, the data held in thecurrent value storage circuit 274, the initial value storage circuit 275and the flag storage circuit 284 are all reset to the initial value “0”.While the data at the reference value storage circuit 278 in FIG. 6 arenot initialized to “0”, they may also be reset to “0”. However, if thecontents of the data held at the reference value storage circuit 278 arereset to “0”, new diagnosis reference values to be used in the subjectintegrated circuit while independently executing the measurement and thediagnosis, as shown in FIG. 4, following the RES signal generation, needto be set promptly at the reference value storage circuit 278. In orderto avoid such a complication in the operational procedure, the referencevalue storage circuit 278 in the embodiment adopts a circuit structurein which the contents of the data held therein are not altered inresponse to the RES signal. Since the attribute of the data held at thereference value storage circuit 278 is such that the data values do notchange frequently, the previous values may be directly utilized. If theyneed to be adjusted, they can be individually altered in response toanother communication command 292. In response to the RES signal, thevalue held at the averaging control circuit 263 assumes a predeterminedvalue, e.g., 16. Namely, unless it is adjusted in response to anothercommunication command 292, the averaging circuit will calculate theaverage of 16 measurement values.

As the wake-up command is output from the command processing circuit344, the startup circuit 254 in FIG. 4 is started up and themeasurement/diagnosis operation starts. As a result, power consumptionat the subject integrated circuit increases. If, on the other hand, asleep signal is output from the command processing circuit 344, theoperation of the startup circuit 254 in FIG. 4 stops and thus, themeasurement/diagnosis operation also stops. Under these circumstances,the power consumption at the subject integrated circuit decreasesmarkedly.

Next, the data write/modification executed in response to acommunication command 292 is described in reference to FIG. 6. Theidentifier 328 in the communication command 292 indicates a specificintegrated circuit to be selected. If the data 300 constitute a datawrite instruction for writing data into an address register 348 or thereference value storage circuit 278 or a data write instruction forwriting data into the averaging control circuit 263 or the selectioncircuit 286, the command processing circuit 344 specifies the writetarget based upon the instruction contents and writes data 330 into thewrite target register.

The address register 348 holds the address of the subject integratedcircuit and the address of the subject integrated circuit is determinedbased upon the contents of the data held at the address register. Thecontents of the data held at the address register 348 are set to 0 inresponse to the RES signal, thereby setting the address of the subjectintegrated circuit to “0”. As the contents of the data held at theaddress register 348 are modified in response to a new instruction, theaddress of the subject integrated circuit is switched to thatcorresponding to the modified contents.

Based upon the communication command 292, the contents of the data heldat the reference value storage circuit 278, the flag storage circuit284, the averaging control circuit 263 and the selection circuit 286 inFIG. 6, as well as the contents of the data stored at the addressregister 348, can be modified. As a modification target circuit amongthese circuits is specified, the contents of the data 330 indicating amodified value are provided to the modification target circuit via adata bus 294, thereby modifying the contents of the data held at thetarget circuit. The circuit in FIG. 6 executes operation based upon themodified data.

The communication command 292 contains a transmission instruction fortransmitting data held inside the integrated circuit. The transmissiontarget data are specified based upon the instruction in the identifier328. For instance, if an internal register in the current value storagecircuit 274 or the reference value storage circuit 278 is specified, thecontents of the data held at the specified register are transferred viathe data bus 294 to the transmission register 302 where they are held inthe circuit for the data 310. They are then transmitted as the requesteddata contents. Thus, the battery controller 20 in FIG. 1 is able to takein a measurement value from a specific integrated circuit or a flagindicating the state of the integrated circuit by issuing thecommunication command 292.

(Setting Addresses of the Integrated Circuits)

The address registers 348 in the individual integrated circuits 3A, . .. , 3M, . . . and 3N are each constituted with a highly reliablevolatile memory and the integrated circuits assume a structure thatallows a new address to be set whenever the contents of the volatilememory become lost or the contents of the data held in the volatilememory become unstable. For instance, when the cell controller 80 startsexecution, the battery controller 20 may transmit a command forinitializing the address registers 348 at the individual integratedcircuits. In response to this command, the address registers 348 at theintegrated circuits are initialized to, for instance, “0” and then a newaddress is set at each integrated circuit. The new address is set ateach of the integrated circuits 3A, . . . , 3M, . . . and 3N as anaddress setting command originating from the battery controller 20 istransmitted to the individual integrated circuits 3A, . . . , 3M, . . .and 3N.

Since the addresses of the individual integrated circuits 3A, . . . ,3M, . . . and 3N can be set in response to a command, the integratedcircuits do not need to include an address setting terminal or externalwiring to be connected to the address setting terminal. In addition,since the addresses can be set through communication command processing,a higher level of control freedom is afforded.

FIG. 8 presents an example of a procedure through which addresses may beset at the address registers 348 of the integrated circuits 3A, . . . ,3M, . . . and 3N in response to a communication command 292 issued fromthe battery controller 20. FIG. 9 illustrates the operation executed inthe circuit shown in FIG. 7 based upon the communication command 292transmitted as shown in FIG. 8. In FIG. 8, the integrated circuits 3A, .. . , 3M, . . . and 3N are indicated as integrated circuits IC1, IC2,IC3, . . . ICn-1 and ICn assuming a positional arrangement matching theorder in which the communication command 292 is transmitted/received.Addresses 1, 2, 3, . . . n-1 and n are respectively set for IC1, IC2,IC3, . . . ICn-1 and ICn through the following method. The numeralassigned to a given integrated circuit IC matches the correspondingaddress number so as to simplify the explanation provided below.However, it is not necessary that they match.

FIG. 8 illustrates the flow of messages carried in the communicationcommand 292 as it is passed on among the battery controller 20 and theindividual integrated circuits IC. FIG. 8 also indicates the contents ofthe data held at the address registers 348 and the contents of the data310 held at the transmission registers 302 within the individualintegrated circuits IC. First, a communication command 292 forinitializing the address registers 348 in all the integrated circuits istransmitted from, for instance, the cell controller 80, therebyinitializing the address registers 348 in the integrated circuits to“0”. FIG. 8 does not include an illustration of this process. Throughthis operation, the address registers 348 at the integrated circuitsIC1, IC2, IC3, . . . and ICn-1 are made to hold the initial value, i.e.,“0”. Upon receiving the communication command 292 for initializing theaddress registers 348 in all the integrated circuits, as shown in FIG.9, the integrated circuit IC1 holds the communication command 292 at thereception register 322. A command decode circuit 345 in the commandprocessing circuit 344 takes in the contents of the identifier 328 andinitializes the address register 348 based upon the initializationmessage. The contents of the identifier 328 are directly set at theidentifier 308 at the transmission register 302 and are then transmittedto the succeeding integrated circuit IC2. The integrated circuits ICexecute this operation in sequence upon receiving the communicationcommand 292 for initializing the address registers 348 and, as a result,the address registers at all the integrated circuits IC becomeinitialized. Ultimately, the command is sent back from the integratedcircuit ICN to the battery controller 20 which is then able to verifythat the address registers 348 in all the integrated circuits IC havebeen initialized.

Based upon the verification described above, a new address issubsequently set at each integrated circuit IC. More specifically, thebattery controller 20 transmits a communication command 292 carrying amessage “set the instruction execution target address to “0”, set thevalue indicated by the data 330 to “0” and set a value obtained byadding “1” to the value of the data 330 for the address register 348 andthe transmission data 310”. This communication command 292 is input tothe reception register 322 of the integrated circuit IC1 taking up thefirst position in the transmission path 52. The data segmentcorresponding to the identifier 328 in the communication command 292 isthen taken into the command decode circuit 345. Since the addressregister 348 in the integrated circuit IC1 holds data indicating “0” atthe time of the reception, (1) the value obtained by adding “1” to “0”indicated by the data 330 is set at the address register 348 and (2) thesum resulting from the addition is set as the data 310 at thetransmission register 302.

Based upon the data decoded via the command decode circuit 345 in FIG.9, an arithmetic operation circuit 346 takes in the value “0” indicatedby the data 330 and then adds “1” to the value thus taken in. The resultof the addition, i.e., “1”, is set in the address register 348 and isalso set as the data 310. This operation is now described in referenceto FIG. 8. As the communication command 292 originating from the batterycontroller 20 is received at the integrated circuit IC1, the data at theaddress register 348 in the integrated circuit IC1 assume the value “1”and the data 310 also assume the value “1”. The data 310 in thecommunication command 292, modified to indicate “1” in the integratedcircuit IC1 are then transmitted to the integrated circuit IC2. Theidentifier 308 in the communication command 292 transmitted from theintegrated circuit IC1 remains unchanged from that is the communicationcommand initially transmitted from the battery controller 20 and thecontents of the data 310 alone are modified.

As data indicating “0” are held at the address register 348 in theintegrated circuit IC2, the arithmetic circuit 346 in the integratedcircuit IC2 adds “1” to the value “1” indicated in the data 330 and setsthe sum at the address register 348 and for the data 310 in theintegrated circuit IC2, as shown in FIG. 9. Thus, the value indicated atthe address register 348 in the integrated circuit IC2 is switched from“0” to “2”. As illustrated in FIG. 8, the value indicated at the addressregister 348 in the integrated circuit IC2 is switched from “0” to “2”and the data 310 at the transmission register 302 are modified toindicate “2”. The modified data 310 are then transmitted to thesucceeding integrated circuit IC3. In a similar manner, the valueindicated at the address register 348 in the integrated circuit IC3 isswitched from “0” to “3” and the data 310 in the transmission register302 in the integrated circuit IC3 are modified to indicate “3”.

Subsequently, the operation described above is repeatedly executed insequence and eventually the value indicated at the address register 348in the integrated circuit ICn-1 is switched from “0” to “n-1” and thedata 310 in the transmission register 302 in the integrated circuitICn-1 are modified to indicate “n-1”. The data indicating “n-1” are thentransmitted to the succeeding integrated circuit ICn. The value held atthe address register 348 of the integrated circuit ICn is switched from“0” to “n” and the data 310 at the transmission register 302 aremodified to indicate “n”. The communication command 292 is then returnedfrom the integrated circuit ICn to the battery controller 20. Since thedata 330 in the returned communication command 292 have been modified toindicate “n”, the battery controller 20 is able to verify that theaddress setting operation has been executed correctly.

At the address registers 348 in the individual integrated circuits IC1,IC2, IC3, IC4, . . . , ICn-1 and ICn, 1, 2, 3, 4, . . . , n-1 and n arerespectively set in sequence through this procedure.

The integrated circuits in the embodiment all have a function with whichthe address registers 348 at the individual integrated circuits arereset to the initial value (0), and thus, the address setting operationcan be executed reliably.

(Another Embodiment of Address Setting)

In reference to FIG. 10, another embodiment that may be adopted whensequentially setting addresses by transmitting a communication command292 from the battery controller 20 to the integrated circuits IC1, IC2,IC3, IC4, . . . , ICn-1 and ICn in FIG. 9 is explained.

First, as in the operation described in reference to FIGS. 8 and 9, acommunication command 292 carrying a message “initialize the contents inthe address registers 348 of all the integrated circuits to, forinstance, ‘0’” is transmitted from the battery controller 20 so as toreset the contents of the data held in the address registers 348 of allthe integrated circuits to “0”. Next, in step 1 in FIG. 10, the batterycontroller 20 transmits a communication command 292 carrying a message“designate an integrated circuit with its address set at ‘0’” (initialvalue) as a target, change the contents of the data held in the addressregister 348 thereof to ‘1’ and thus set the address of the targetintegrated circuit to which the transmitted communication command 292 isdirected to ‘1’”. In this situation, the address of the targetintegrated circuit to which the transmitted communication command 292 isdirected may be set to a value other than “1” as long as it is set to avalue other than “0” (initial value).

As shown in FIG. 1, the integrated circuit that receives thecommunication command 292 first is the integrated circuit IC1 (3A)assuming the first position in the transmission path 52. At thecommunication circuit 127 of the integrated circuit IC1 structured asshown in FIG. 7, the communication command 292 is held in the receptionregister 322. Since the address register 348 in the integrated circuitIC1 already indicates “0” (initial value), the command processingcircuit 344 judges based upon the identifier 328 that the integratedcircuit IC1 is a target integrated circuit where the communicationcommand 292 is to be executed as indicated in the message therein. Asindicated in the message in the communication command 292, the commandprocessing circuit 344 modifies the contents in the address registers348 to “1”. Then, the contents in the identifier 308 in the transmissionregister 302 are modified so as to switch the address of the targetintegrated circuit to execute the communication command 292 to “1”. Themodified communication command 292 is transmitted from the transmissionterminal TX to the succeeding integrated circuit IC2.

The contents of the address of the data held in the address register 348of the integrated circuit IC2 that receives the communication command292 next indicate “0” (initial value) and accordingly, the commandprocessing circuit 344 in the integrated circuit IC2 judges that theintegrated circuit IC2 is not a target integrated circuit to execute thecommunication command. Thus, the received communication command 292 isdirectly set in the transmission register 302 and the unalteredcommunication command 292 is transmitted to the subsequent integratedcircuit. At the integrated circuit IC3 and all subsequent integratedcircuits IC, where the contents of the data held in the addressregisters 348 invariably indicate “0” (initial value), the subjectintegrated circuits are each judged not to be a target integratedcircuit to execute the communication command. Consequently, thecommunication command 292 is returned to the battery controller 20without any of the subsequent integrated circuits executing thecommunication command.

Upon verifying that the communication command 292 has been returned, thebattery controller 20 transmits in step 2 in FIG. 10 a communicationcommand 292 carrying a message “designate an integrated circuit with theaddress thereof indicating ‘0’ (initial value), modify the contents inthe address register 348 to ‘2’ and set the address of the targetintegrated circuit to which the transmitted communication command 292 isdirected to ‘2’”. In this situation, the address of the targetintegrated circuit to which the transmitted communication command 292 isdirected may be set to a value other than “2” as long as a given addresssetting is not replicated. The contents of the data held in the addressregister 348 of the integrated circuit IC1 that receives thecommunication command 292 first indicate “1” and accordingly, thecommand processing circuit 344 in the integrated circuit IC1 judges thatthe integrated circuit IC1 is not a target integrated circuit to executethe communication command. Thus, the received communication command 292is directly transmitted to the succeeding integrated circuit IC2.

The value indicated at the address register 348 in the integratedcircuit IC2 that receives the communication command next is “0” and,accordingly, its command processing circuit 344 executes thecommunication command 292, sets “2” at the address register 348,modifies the address of the target to execute the communication command292 to “2” and then transmits the communication command to thesubsequent integrated circuit. Since the values held at the addressregisters 348 at the integrated circuits IC3 and all subsequentintegrated circuits are invariably “0” and thus none of these integratedcircuits is an execution target, the communication command 292 isreturned to the battery controller 20 without any of the subsequentintegrated circuits executing the communication command.

Subsequently, as the battery controller 20 transmits communicationcommands 292 in sequence, the contents of the address register 348 inthe integrated circuit IC3 are modified from “0” to “3”, the contents ofthe address register 348 in the integrated circuit IC4 are modified from“0” to “4” and so forth, until the contents in the address register 348of the integrated circuit ICn are modified from “0” to “n”.

(Adjustment of the States of Charge SOCS)

FIG. 11 presents a flowchart of the processing through which the statesof charge SOCs at the battery cells in the battery unit 9 are measured,battery cells charged to significant extents are selected, the requireddischarge time is determined through arithmetic operation for each ofthe selected battery cells and the battery cells are dischargedaccordingly. In the figure, the operation executed at each integratedcircuit is indicated on the left side and the operation executed at thebattery controller 20 is indicated on the right side.

In step 400 in FIG. 11, the battery controller 20 transmits acommunication command 292 for the integrated circuit 3A designated asthe command target, requesting that the voltages at the battery cells inthe initial state be read. As the integrated circuit 3A receives thecommunication command 292, the command processing circuit 344 in FIG. 7sets the contents held at the initial value storage circuit 275 as thedata 310 in the transmission register 302 and the data thus set aretransmitted to the next integrated circuit (step 410).

The battery controller 20 then designates the integrated circuitsucceeding the integrated circuit 3A for the read of the voltages at thebattery cells in the initial state. It further takes in the data fromthe integrated circuits 3M and 3N in sequence. Consequently, the voltagevalues at all the battery cells in the battery unit 9 in the initialstate are taken in from the initial value storage circuit 275 of theindividual integrated circuits.

Next, in step 420, the battery controller 20 takes in the values of thevoltages measured at all the battery cells in the battery unit 9 anddetermines through arithmetic operation the state of charge SOC of eachbattery cell based upon the information thus taken in. The average ofthe values having been determined through the arithmetic operation isthen calculated and, in step 430, the length of time over which thecorresponding balancing switch among the balancing switches 129A˜129D,needs to remain in a continuous state in order to adjust the SOC of anybattery cell indicating a value greater than the average value iscalculated. The length of time over which the balancing switch 129A,129B, 129C or 129D is to remain in the continuous state may bedetermined through any of various methods other than that describedabove. Through any of these methods, the length of time over which thebalancing switch 129A, 129B, 129C or 129D correlated to the battery cellwith the SOC thereof indicating a large value is to remain in thecontinuous state can be determined.

Next, in step 440, the battery controller 20 transmits a communicationcommand 292 containing information indicating the length of time thebalancing switch is to remain in the continuous state to thecorresponding integrated circuit.

In step 450, the integrated circuit, having received the informationindicating the required length of time sets the balancing switch in thecontinuous state based upon the command.

In step 460, the length of time elapsing while the balancing switchremains in the continuous state is measured. In step 470, the length oftime having elapsed in the continuous state is compared with therequired length of time over which the particular balancing switch needsto remain in the continuous state and a decision is made as to whetheror not the measured value indicating the elapsed time has become equalto the required length of time having been calculated. Once the measuredvalue indicating the elapsed time becomes equal to the required lengthof time calculated for the particular balancing switch, the operationshifts into the next step 480.

In step 480, the battery controller 20 transmits a communication command292 to the corresponding integrated circuit for opening the balancingswitch having remained in the continuous state over a length of timematching the calculated length of power supply time. In response to thiscommunication command 292, in step 490, the corresponding integratedcircuit sets the target balancing switch specified in the communicationcommand 292 in the open state by stopping the drive signal originatingfrom a switch drive circuit 133. As a result, the discharge of thecorresponding battery cell stops.

(Test Executed to Determine Whether or Not the Individual IntegratedCircuits and the Like are in an Abnormal State)

FIG. 12 presents a flowchart of the processing executed to test whetheror not the individual integrated circuits 3A, . . . , 3M, . . . and 3Nor the individual battery cells are in an abnormal state. In the figure,the operation executed in each of the integrated circuits 3A, . . . ,3M, . . . and 3N is indicated on the left side and the operationexecuted at the main controller 20 is indicated on the right side.

In step 500, the battery controller 20 transmits a communication commandfor state (abnormality) detection to the integrated circuit 3A. Next, instep 510, the state (abnormality) detection communication command istransmitted from the integrated circuit 3A to be passed on to theintegrated circuits . . . , 3M, . . . and 3N in sequence before it isultimately returned to the battery controller 20.

In step 520, the battery controller 20 receives state (abnormality)information having been transmitted from the individual integratedcircuits and verifies the states (abnormality) indicated in the receivedinformation. Next, in step 530, the battery controller 20 makes adecision as to whether or not an abnormality has occurred at any of theintegrated circuits 3A, . . . , 3M, . . . and 3N or whether or not anabnormality has occurred at any of the battery cells BC1˜BC4 in eachgroup. If it is decided that no abnormality has occurred at anyintegrated circuit or the corresponding battery cells, the flow ends.However, if it is decided that an abnormality has occurred at any of theintegrated circuits 3A, . . . , 3M, . . . and 3N, the operation shiftsinto step 540.

In step 540, the battery controller 20 transmits a communication commandfor state (abnormality details) detection to determine the particularsof the abnormality by specifying the address of the integrated circuitwhere the abnormality has occurred.

In step 550, the integrated circuit with the specified address transmitsthe measurement value attributed to the abnormal state (abnormalitydetails) or the diagnosis results indicating the abnormal state. Instep560, the battery controller 20 verifies the integrated circuit where theabnormality has occurred and the cause of the abnormality. Once thecause of the abnormality is verified, the processing in FIG. 12 ends.Subsequently, based upon the cause of the abnormality, a decision ismade as to whether or not to supply the DC power from the lithiumbatteries or whether or not to charge the lithium batteries withgenerated power. In the event of an abnormality, the power supply isstopped by setting the relay disposed between the DC power supply systemand the electrical load such as the inverter in the open state.

(Automotive Power Supply System)

FIG. 13 is a circuit diagram of the DCpower supply system describedabove in reference to FIG. 1, adopted in a drive system for anautomotive rotating electrical machine. A battery module 900 includesthe battery unit 9, the cell controller 80 and the battery controller20. It is to be noted that the battery cells constituting the batteryunit 9 in FIG. 13 are divided into two blocks, a high potential-sideblock 10 and a low-potential-side block 11. The high potential-sideblock 10 and the low-potential-side block 11 are connected in series viaan SD (service disconnect) switch 6, which is constituted by seriallyconnecting a switch and a fuse and is installed for purposes ofmaintenance/inspection.

The positive pole of the high potential-side block 10 is connected tothe positive pole of an inverter 220 via a positive pole high-rate cable81 and a relay RLP. The negative pole of the low-potential-side block 11is connected to the negative pole of the inverter 220 via a negativepole high-rate cable 82 and the relay RLN. The high potential-side block10 and the low-potential-side block 11, connected in series via the SDswitch 6 together constitute a high-rate battery (a battery in a powersupply system constituted by connecting in series two battery units 9)with a nominal voltage of, for instance, 340 V and a capacity of 5.5 Ah.It is to be noted that the rated current of the fuse in the SD switch 6may be, for instance, approximately 125 A. By adopting this structure,an even higher level of safety is assured.

As described earlier, the relay RLN is disposed between the negativepole of the low-potential-side block 11 and the inverter 220 and therelay RLP is disposed between the positive pole of the highpotential-side block 10 and the inverter 220. A parallel circuitconstituted with a resistor RPRE and a pre-charge relay RLPRE isconnected in parallel to the relay RLP. A ammeter Si such as a Hallelement or the like, which is installed in a junction box, is insertedbetween the positive pole-side main relay RLP and the inverter 220. Itis to be noted that the output line of the ammeter SI is led out to thebattery controller 20 so as to enable the inverter 220 to constantlymonitor the quantity of current supplied from the lithium battery DCpower source.

The rated current of the relays RLP and RLN may be approximately 80 A,whereas the rated current of the pre-charge relay RLPRE may beapproximately 10 A. In addition, a resistor with a rated capacity of 60W and assuming a resistance value of approximately 50Ω may be utilizedas the resistor RPRE. The rated current of the ammeter Si may beapproximately +200 A.

The negative pole high-rate cable 82 and the positive pole high-ratecable 81 are connected to the inverter 220 that drives a motor 230 of ahybrid vehicle, via the relay RLP and the relay RLN respectively andalso via the output terminal of the battery module 900. This structureassures a high level of safety.

The inverter 220 is constituted with a power module 226, an MCU 222, adrive circuit 224 via which the power module 226 is driven and a largecapacity smoothing capacitor 228 with a capacity of approximately 700μF˜2000 μF. The power module 226 constitutes an inverter that convertsthe DC power supplied from the high-rate battery power source with anominal voltage of 340 V to three-phase AC power to be used to drive themotor 230. A smoothing capacitor 228 constituted with a film capacitorrather than an electrolytic capacitor will provide bettercharacteristics. The environment surrounding the vehicle is a factorthat determines the condition under which the smoothing capacitor 228installed in the vehicle operates. The smoothing capacitor 228 is likelyto operate over a wide temperature range of, for instance, from a lowtemperature such as −20° C. or −30° C. to 100° C. When the temperaturebecomes lower than 0° C., the characteristics of an electrolyticcapacitor will drastically deteriorate and its voltage noise removalperformance will be negatively affected. Under such circumstances, theintegrated circuits shown in FIGS. 1 and 2 may be subjected to verysignificant noise. The characteristics of a film capacitor, on the otherhand, are not significantly compromised even at very low temperaturesand thus, voltage noise applied to the integrated circuits can beeffectively reduced with the film capacitor.

In response to an instruction issued from a higher-order controller 110,the MCU 222 charges the smoothing capacitor 228 by first switching thenegative pole-side relay RLN from the open state to the closed state andthen switching the pre-charge relay RLPRE from the open state to theclosed state to drive the motor 230. Subsequently, it switches thepositive pole-side relay RLP from the open state to the closed statethereby starting power supply from the high-rate batteries in thebattery module 900 to the inverter 220. It is to be noted that whenbraking the hybrid vehicle, the inverter 220 executes regenerativebraking control by controlling the phase of the AC power generated atthe power module 226 relative to the rotor of the motor 230 and engagingthe motor 230 in operation as a generator, so as to charge the high-ratebatteries with the power regenerated through generator operation. If thestate of charge at the battery unit 9 becomes lower than the referencelevel, the inverter 220 engages the motor 230 in operation as a powergenerator and charges the battery unit 9. The three-phase AC powergenerated at the motor 230 is converted to DC power via the power module226 and the DC power resulting from the conversion is then supplied tothe battery unit 9 constituted with the high-rate battery.

As described above, the inverter 220, which includes the power module226, executes DC/AC power conversion. When the motor 230 is to beengaged in operation as a motor in response to an instruction issued bythe higher-order controller 110, the drive circuit 224 is controlled soas to generate a rotating magnetic field along the advancing directionrelative to the rotation of the rotor in the motor 230 in order tocontrol the switching operation at the power module 226. In thissituation, DC power is supplied from the battery unit 9 to the powermodule 226. The drive circuit 224 may instead be controlled so as togenerate a rotating magnetic field along the retarding directionrelative to the rotation of the rotor in the motor 230 to control theswitching operation at the power module 226. Under such circumstances,power is supplied from the motor 230 to the power module 226 and DCpower from the power module 226 is then supplied to the battery unit 9.As a result, the motor 230 functions as a power generator.

The power module 226 in the inverter 220 executes on/off operation athigh speed to achieve DC/AC power conversion. At this time, a largeelectric current may be cut off at high-speed and, in such a case, asignificant voltage fluctuation will occur due to the inductance of theDC circuit. The large capacity smoothing capacitor 228 is installed inthe DC circuit in order to inhibit such a voltage fluctuation. The heatgenerated at the power module 226 poses a serious problem in the onvehicle inverter 220 and the speed with which the power module 226 isswitched into the continuous state and the cut off state must beincreased in order to inhibit heat generation. However, if the operationspeed is raised, the extent to which the voltage jumps due to inductancealso increases, which, in turn, generates more noise. For this reason,the smoothing capacitor 228 tends to assume a greater capacity.

At the start of operation of the inverter 220, the smoothing capacitor228 holds substantially no electrical charge and, as the relay RLP isclosed, a large initial current starts to flow in. Since the largeinitial current flows into the smoothing capacitor 228 from thehigh-rate battery, the negative pole-side main relay RLN and thepositive pole-side main relay RLP may become fused and damaged. In orderto prevent this, the MCU 222 first switches the negative pole-side relayRLN from the open state to the closed state, switches the pre-chargerelay RLPRE from the open state to the closed state while holding thepositive pole-side relay RLP in the open state and charges the smoothingcapacitor 228 by regulating the maximum current via the resistor RPRE.Once the smoothing capacitor 228 is charged to a predetermined voltage,the initial state is cleared and the negative pole-side relay RLN andthe positive pole-side relay RLP are set in the closed state so as tosupply the DC power from the battery module 900 to the power module 226without engaging the pre-charge relay RLPRE or the resistor RPRE inoperation. Under this control, the relay circuit is effectivelyprotected and the maximum current that may flow through the lithiumbattery cells and the inverter 220 is regulated so as not to exceed apredetermined value, thereby assuring a high level of safety.

Since the occurrence of noise voltage can be inhibited by reducing theinductance in the DC-side circuit of the inverter 220, the smoothingcapacitor 228 is disposed in close proximity to a DC-side terminal ofthe power module 226. In addition, the smoothing capacitor 228 itselfassumes a structure that reduces the inductance. As the smoothingcapacitor 228 structured as described above undergoes the initialcharge, a large electrical current flows in momentarily and significantheat generated at this time may damage the smoothing capacitor. However,the extent of such damage can be lessened via the pre-charge relay RLPREand the resistor RPRE. While the MCU 222 controls the inverter 220, theinitial charge of the smoothing capacitor 228 is also executed undercontrol of the MCU 222.

A capacitor CN is inserted between a connecting cable, which connectsthe negative pole of the high-rate battery in the battery module 900with the negative pole-side relay RLN, and the case ground (assuming apotential equal to that at the vehicle chassis). A capacitor CP isinserted between a connecting cable, which connects the positive pole ofthe high-rate battery with the positive pole-side relay RLP, and thecase ground. The capacitors CN and CP are installed in order to preventerroneous operation of the low-rate electrical circuit and destructionof the integrated circuit IC constituting the cell controller 80 due toa surge voltage, by eliminating noise generated via the inverter 220.While the inverter 220 includes a noise removal filter, the capacitorsCN and CP are installed so as to even more effectively prevent erroneousoperations of the battery controller 20 and the cell controller 80 andimprove the noise withstanding reliability of the battery module 900. Itis to be noted that in FIG. 13, the high-rate electrical circuit in thebattery module 900 is indicated by the bold line. The high-rateelectrical circuit is wired by using a flat copper wire with a largesectional area.

It is to be noted that a blower fan 17 in FIG. 13, which cools thebattery unit 9, is engaged in operation via a relay 16 that is turned onin response to a command from the battery controller 20.

(Operational Flow in the Automotive Power Supply System)

FIG. 14 presents a flowchart of the operation executed in the automotivepower supply system shown in FIG. 13. The following is a step by stepdescription of the operational flow.

In step 801, as the key switch in the vehicle is turned on to start theengine, a specific operation is performed to switch the vehicle in astationary state to a traveling state or the integrated circuits shiftfrom the sleep state to the wake-up state. Then instep 802, the batterycontroller 20 is started up and initialized.

Next, CAN communication is executed in step 803. As a result, a blankmessage is output to each controller so as to verify the state ofcommunication among the individual control devices. In step 804, thebattery controller 20 transmits a startup/initialization communicationcommand 292 to the cell controller 80.

Upon receiving the communication command 292, the integrated circuits3A, . . . , 3M, . . . and 3N each enter the wake-up state, the startupcircuit 254 in FIG. 4 in each integrated circuit starts operation andthe address registers 348 in the individual integrated circuits areinitialized based upon the output from the command processing circuits344 described in reference to FIG. 7. Subsequently, new addresses areset at the individual integrated circuits IC as has been explained inreference to FIGS. 8 and 10.

In step 805, the voltage and the current at the overall batteryconstituted with the individual battery cells all connected in seriesare respectively detected via the voltmeter Vd and the ammeter Si shownin FIG. 1 and the outputs are input to the battery controller 20. Inaddition, a temperature sensor (not shown) measures the temperature.

In addition, as the startup/initialization communication command 292 isreceived at the cell controller 80 in step 804 and each of theintegrated circuits 3A, . . . , 3M, . . . and 3N receives thecommunication command 292, the first stage counter 256 and the secondstage counter 258 at each integrated circuit described in reference toFIG. 4, start operation (step 806) and the measurement operation isexecuted repeatedly as indicated in the operation table 260 (step 807).As has been described in reference to FIGS. 4 and 6, the integratedcircuits each measure the terminal voltages at the battery cells thereinin step 807. The measurement values thus obtained are then stored intothe current value storage circuit 274 and the initial value storagecircuit 275 (step 808). Based upon the results of the battery cellvoltage measurement executed in step 807, the integrated circuits eachmake a decision in step 809 with regard to whether or not any of thebattery cells is over-charged or over-discharged. In the event of anabnormality, the diagnosis flag is set in the flag storage circuit 284in FIG. 6 and thus, the battery controller 20, detecting the diagnosisflag, is able to detect the abnormality. Since the individual integratedcircuits execute the battery cell voltage measurement and the batterycell abnormality diagnosis independently of one another, the states ofall the battery cells can be diagnosed quickly even if the battery unit9 is constituted with numerous battery cells. Consequently, the statesof all the battery cells are diagnosed before turning on the relays RLPand RLN, assuring a high level of safety.

Upon verifying that the state of each battery cell has been detected instep 810, the initialization is completed in step 811 and also, it isverified that no abnormal state exists if no diagnosis flag has been setin a flag storage circuit 284. Once it is verified that no abnormalityhas occurred, the relay RLN in FIG. 13 is closed, then the relay RLPREis closed and finally the relay RLP is closed. As the relays are closed,the DC power supply from the battery unit 9 to the inverter 220 starts.

The length of time to elapse between step 801 in which the key switch isturned on and the time point at which the power supply is enabled can beset to approximately 100 ms or less. Since the DC power supply isenabled quickly, as described above, the driver's desire to start thevehicle immediately is fully satisfied.

Furthermore, during this very short period of time, addresses are set atthe various integrated circuits, the integrated circuits each measurethe voltages at all the battery cells in the corresponding group, themeasurement results are stored into the initial value storage circuit275 shown in FIG. 6 and the abnormality diagnosis is completed.

The voltages at the battery cells are measured before the relays RLP,RLN and RLPRE are turned on, i.e., before the inverter 220 and thebattery unit 9 become electrically connected with each other. In otherwords, the voltages at the battery cells are measured before startingthe power supply to the inverter 220 and thus, accurate detection of thestates of charge SOCs is enabled based upon the terminal voltages at thebattery cells measured prior to the current supply.

Subsequently, the operation enters a normal mode in step 812 and thevoltages, the currents and the temperatures at the individual cells aremeasured in step 813. The measurement is executed through communicationwith the cell controller 80 instep 812. It is to be noted that thetemperatures are measured based upon the outputs from temperaturesensors (not shown).

Then, based upon the measurement values indicating the voltages and thecurrents at the individual battery cells measured prior to the currentsupply start, and also based upon the temperature measurement values asnecessary, the required lengths of discharge time (balancing time) arecalculated in step 815. Based upon the calculation results, informationindicating the lengths of time over which the balancing switches129A˜129D in FIG. 2 are to remain in the continuous state is transmittedto each integrated circuit. Instep 816, the integrated circuits eachexecute control under which the balancing switches remain closed basedupon the required lengths of time over which they are to remain in thecontinuous state. This operation is executed through the flow shown inFIG. 11.

Instep 817, a test is executed to determine whether or not anabnormality has occurred at any of the integrated circuits 3A˜3N or atany of the battery cells. Next, in step 818, the state of each batterycell, indicating the remaining power available therein, the extent ofdegradation of the battery cell or the like is determined througharithmetic operation.

In step 818, a decision is made as to whether or not the length of timecounted for each target balancing switch among the balancing switches129A˜129D has become equal to the corresponding required length of timeover which the balancing switch is to remain in the continuous state,having been determined through the arithmetic operation. If the measuredlength of time is still not equal to the required length of time, theoperation returns to step 813 to repeatedly calculate the requiredlength of balancing time in step 816, execute the test in step 817 anddetermine the state of each battery cell through arithmetic operation instep 818.

Once it is decided in step 818 that the length of time measured for thetarget balancing switch 129A, 129B, 129C or 129D has become equal to therequired length of time over which it is to remain in the continuousstate, an instruction for stopping the discharge operation by settingthe target balancing switch 129A, 129B, 129C or 129D having remained inthe continuous state over the required length of time, is set in theopen state is transmitted from the battery controller 20 to thecorresponding integrated circuit. Since the discharge control, underwhich the target balancing switch is closed for discharge, isselectively executed only for battery cells indicating high SOC levelsin the battery unit 9, the balancing switches for battery cells with lowSOC values remain in the open state throughout. As explained earlier,the state of charge SOC in each battery cell in the battery unit 9 isdetermined through arithmetic operation, the required length of timeover which the balancing switch corresponding to each battery cell is toremain in the continuous state is calculated and the required length oftime thus calculated is held in a storage device at the batterycontroller 20. Since the required length of time over which eachbalancing switch is to remain in the continuous state is determinedbased upon the SOC of the corresponding battery cell, varying lengths oftime are normally calculated for the individual balancing switches. Itis naturally conceivable that there are battery cells that do notrequire the corresponding balancing switches to be set in the continuousstate at all. For this reason, the length of time over which power is tobe supplied to each battery cell is compared to the length of timehaving been counted in correspondence to the particular battery cell instep 818 and a command for stopping discharge of the battery cell havingbeen supplied with power over the required length of time is transmittedto the integrated circuit controlling the discharge of the specificbattery cell.

(Communication End Sequence)

FIG. 15 illustrates the sequence through which the communication betweenthe battery controller 20 and the cell controller 80 in the automotivepower supply system shown in FIGS. 1 and 13 may be terminated.

FIG. 15( a) indicates the timing with which the power supply via thepower (Vc) terminal of the battery controller 20 is stopped. FIG. 15( b)indicates the timing with which the power supply at the photocouplers PH1 and PH 2 in the entry-side interface INT(E) constituting an insulatingcircuit and the photocouplers PH 3 and PH 4 in the exit-side interfaceINT(O) constituting another insulating circuit stops. FIG. 15( c)indicates the timing with which transmission to and reception from thebattery controller 20 via the TX terminals and the RX terminals stops.FIG. 15( d) indicates the timing with which output of a signaloriginating from the battery controller 20 and transmitted via thewake-up terminal stops.

As the figure clearly indicates, transmission to and reception from thebattery controller 20 via the TX terminals and the RX terminals arefirst stopped. Then, if a signal from the battery controller 20 providedvia the wake-up terminal is being used in the system, the transmissionof the signal is stopped. Next, the power supply is stopped at the power(VC) terminal of the battery controller 20 and subsequently, the powersupply to the photocouplers PH 1 and PH 2 in the entry-side interfaceINT(E) constituting an insulating circuit and the photocouplers PH 3 andPH 4 at the exit-side interface INT(O) constituting an insulatingcircuit is also stopped.

By stopping the operation at the individual units in this order, theintegrated circuits can be set into the sleep state reliably.

It is to be noted that FIG. 16 illustrates the operation in a systemthat does not utilize a signal provided through a wake-up terminal,unlike the system whose operation is illustrated in FIG. 15. Since asignal provided through the wake-up terminal is not utilized, the signaltransmission does not need to be stopped, unlike in the system in theother system in which the signal transmission is stopped with the timingindicated in FIG. 15( d). The other aspects of the operational sequenceare identical to those in FIG. 15.

(Structures of Individual Integrated Circuits and Battery Cells in theCorresponding Groups)

In the embodiment described earlier, all the battery cell groups aremade up with equal numbers of battery cells with four battery cellsconnected to each of the integrated circuits 3A, . . . , 3M, . . . and3N corresponding to specific battery cell groups. The integratedcircuits 3A, 3M, . . . and 3N each obtain information indicating thevoltages and the like from the four battery cells connected thereto andeach control charge/discharge of the four battery cells therein. Inother words, the integrated circuits 3A, . . . , 3M, . . . and 3N handleequal numbers of battery cells.

Alternatively, the various battery cell groups in the battery unit 9 maybe made up with different numbers of battery cells, as shown in FIG. 17.In such a case, the overall number of battery cells to constitute thebattery unit 9 can be selected freely without having to limit it to amultiple of the number of groups. FIG. 17( a) indicates the numbers ofbattery cells making up the individual groups and FIG. 17( b) indicatesthe integrated circuits corresponding to the specific battery cellgroups. In this case, varying numbers of sets of data, indicating thebattery cell terminal voltages, will be held at the current valuestorage circuits 274 and the initial value storage circuits 275installed in the individual integrated circuits. While varying numbersof sets of data may be transmitted to the battery controller 20 inresponse to a request from the battery controller 20, the data may besorted so that they are transmitted in batches made up with equalnumbers of sets of data, as shown in FIG. 17( c). By transmitting andreceiving such a fixed number of sets of data, as described above, thetransmission reliability can be improved.

As indicated in FIG. 17( b), the battery cell groups corresponding tothe integrated circuits 3A, . . . , 3M, . . . and 3N are made up withvarying numbers of battery cells. As FIG. 17(a) indicates, the batterycell groups corresponding to the highest-stage integrated circuit 3A andthe lowest-stage integrated circuit 3N each include four battery cells,fewer than the number of battery cells making up the other battery cellgroups. Battery cell groups other than those corresponding to thehighest-stage and lowest-stage integrated circuits in the battery unit 9each include a greater number of battery cells, e.g., 6, then the numberof battery cells constituting the highest-stage and lowest-stage groups.

The integrated circuit 3A assuming the highest potential and theintegrated circuit 3N assuming the lowest potential are connected to thebattery controller 20 via insulating circuits constituted with thephotocouplers PH 1 and PH 4, as explained earlier. It is desirable toset the voltage tolerance of the photocouplers PH 1 and PH 4 to a lowerlevel from the viewpoint of safety and cost performance. By reducing thenumbers of battery cells to constitute the battery cell groupscorresponding to the integrated circuits connected with thephotocouplers PH 1 and PH 4, the required photocoupler voltage tolerancelevel can be lowered. Namely, if six battery cells are connected toconstitute each of the battery cell groups corresponding to thehighest-order integrated circuit 3A and the lowest-order integratedcircuit 3N, the required voltage tolerance of the photocouplersconnected between the integrated circuits and the battery controller 20will need to be greater than the highest terminal voltage among theterminal voltages at the six battery cells. In other words, when abattery cell group is made up with a greater number of battery cells,the required voltage tolerance rises.

The highest-order integrated circuit 3A and the lowest-order integratedcircuit 3N in the embodiment each hold four sets of data indicating theterminal voltages at the four battery cells. Thus, they each exchangedata related to the four battery cells through communication with thebattery controller 20. In addition, the other integrated circuitsincluding the integrated circuit 3M each hold data with data collectedat the six battery cells, which need to be transmitted to the batterycontroller 20.

As indicated in FIG. 17( c), the data related to all the battery cellsare transmitted/received in sequence in units of data corresponding tofour battery cells. Namely, the first batch of data is constituted withthe data related to the four battery cells connected to the integratedcircuit 3A, the next batch of data is constituted with the data relatedto the four battery cells disposed on the highest-stage side among thedata related to the six battery cells connected to the Integratedcircuit at the second stage, the next batch of data is constituted withthe data related to the two battery cells disposed on the lower stageside among the data related to the six battery cells connected to theintegrated circuit at the second stage and the data related to the twobattery cells disposed on the highest-stage side among the data relatedto the six battery cells connected to the integrated circuit at thethird stage, . . . , and the last batch of data is constituted with thedata related to the four battery cells connected to the integratedcircuits 3N at the last stage.

The volume of data that can be transmitted at a time through thecommunication between, for instance, the battery controller 20 and thehigher-order controller 110 in the automotive power supply system shownin FIG. 13 is limited (e.g., the upper limit to the data volume may beequivalent to the data volume corresponding to four battery cells).Accordingly, by adopting the structure shown in FIG. 17( c) for thebattery unit 9, signals can be transmitted/received in a volume neverexceeding the upper limit, so as to assure highly reliable signalexchange.

In the embodiment described above, the uppermost-stage integratedcircuit 3A and the lowermost-stage integrated circuit 3N are eachconnected with four battery cells and other integrated circuits are eachconnected with six battery cells. However, the present invention is notlimited to this example and similar advantages can be achieved as longas fewer battery cells are connected to the uppermost-stage andlowermost-stage integrated circuits 3A and 3N, compared to the number ofbattery cells connected to the other integrated circuits. In addition,if either the uppermost-stage integrated circuit 3A or thelowermost-stage integrated circuit 3N is connected with a smaller numberof battery cells than the other, the voltage tolerance level of thephotocoupler corresponding to the integrated circuit connected with thesmaller number of battery cells can be lowered.

Furthermore, in the embodiment described above, data are exchanged insequence in batches each constituted with data related to four batterycells, even though the varying numbers of battery cells are connected tothe individual integrated circuits. However, the battery cell databatches do not need to be prepared in the four-battery cell units andsimilar advantages can be achieved as long as battery cell data areexchanged in batches prepared in units each corresponding to a number ofbattery cells smaller than the largest number of battery cells among thevarying numbers of battery cells connected to the individual integratedcircuits.

(Battery Module Structure)

FIGS. 18 and 19 present a specific structural example that may beadopted in the battery module 900 constituted with the battery unit 9and the cell controller 80. The battery module 900 includes a cuboidmetal battery case 9 a constituted with an upper lid 46 and a lower lid45. The battery module 900 also includes an output terminal via which DCpower is supplied to a power-consuming device or received from apower-generating device such as the inverter 220. A plurality of batteryassemblies 19 are housed and fixed within the battery case 9 a. Whilenumerous wirings are laid out within the battery case 9 a for purposesof voltage and temperature detection, these wirings are electricallyprotected against external noise with the metal battery case 9 aenclosing the battery module 900. In addition, as explained earlier,since the battery cells are protected via the battery case 9 a and anouter container encasing the battery case, the power supply systemsafety is assured even in the event of a traffic accident.

The battery cells in the embodiment are lithium secondary batteriesassuming a columnar shape, each made up with a positive pole activesubstance constituted of a lithium-manganese double oxide and a negativepole active substance constituted of amorphous carbon. The battery cellsare each encased within a casing achieving a high level of thermalconductivity. While the nominal voltage and the capacity of such abattery cell constituted with a lithium secondary battery arerespectively 3.6 V and 5.5 Ah, the terminal voltage at the battery cellfluctuates as the state of charge changes. The terminal voltage maybecome as low as 2.5 V as the SOC level at the battery cell decreases,whereas it may rise as high as 4.3 V as the SOC level at the batterycell increases.

Since the structure assumed in the battery cells in the embodimentfacilitates connections of a detection harness 32, the high-rate cables81 and 82 and the like, a high level of safety is maintained with evengreater reliability.

As illustrated in FIGS. 18 and 19, two battery blocks 10 and 11 arefixed side-by-side at the lower lid 45. At one end of the lower lid, acell controller box (C/C box) 79 with a built-in cell controller(hereafter referred to as a C/C) 80, to be described in reference toFIG. 20 is fixed via screws. As shown in FIG. 20, the C/C 80 isconstituted with a single substrate assuming a laterally elongated shapewith wirings printed on both sides thereof. The C/C 80 is fixed in theC/C box 79 in an upright orientation with screws threaded through roundholes formed at four positions, i.e., at two positions on the upper sideand two positions on the lower side. The substrate with ICs formedthereupon is disposed so as to face opposite the side surfaces of thebattery cells constituting the battery assemblies, and such a structureallows the entire battery module 900 to be fitted within a relativelysmall space. In addition, the individual battery assemblies and the C/C80 can be wired relatively easily.

Connectors 48 and 49, disposed over a distance from each other at thetwo ends of the substrate constituting the C/C 80 on the left side andthe right side, connect with the individual battery cells constitutingthe battery blocks 10 and 11 via the detection harness 32. A harnessconnector (not shown) mounted on one side of the detection harness 32toward the substrate is connected to the connectors 48 and 49 at the C/C80. Namely, as shown in FIG. 19, the detection harness 32 is installedin correspondence to each of the battery blocks 10 and 11. The C/C 80 isequipped with the two connectors 48 and 49 in correspondence to the twosplit battery blocks 10 and 11 housed within the battery case toconstitute the battery module 900. Since the two battery assembly blocks10 and 11 are connected via the connectors, the maintenance and thewiring operation are facilitated. One of the connectors 48 and 49 isused to connect with the serially connected battery cells on thehigh-voltage side, whereas the other connector 48 or 49 is used toconnect with the serially connected battery cells on the low-voltageside. In other words, the connection between the serially connectedbattery cells and the C/C 80 is achieved over a plurality of blocksbased upon the potentials of the serially connected battery cells so asto connect the battery cells with the C/C 80 via a plurality ofconnectors each corresponding to one of split blocks divided incorrespondence to specific potential levels. Through these measures, thepotential differential manifesting within the connection achieved viathe connectors can be minimized. By adopting this structure, outstandingadvantages with regard to voltage tolerance, prevention of currentleakage and dielectric breakdown are achieved. In addition, whenconnecting or disconnecting the various connectors, all the connectorscannot be connected or disconnected at once, giving rise to a situationin which only some of the connectors are in the connected state during aconnecting or disconnecting process. By adopting the structure describedabove, the difference among the voltages at the individual connectorscan be reduced so as to minimize the adverse electrical effect that maybe attributable to the state of partial connection occurring during theconnecting or disconnecting process.

In addition, a plurality of ICs are formed at the substrate constitutingthe C/C 80, in correspondence to the serially connected battery cellshoused in the battery module 900. The number of battery cells to behandled via a single IC is determined based upon the processingcapability of the IC. In the embodiment, a single IC is utilized incorrespondence to four battery cells. However, a single IC may be usedin correspondence to five or six battery cells instead. Alternatively, asingle system may include a block where ICs are each used incorrespondence to four battery cells and a block where ICs are each usedin correspondence to six battery cells. The total number of seriallyconnected battery cells does not need to be a multiple of the optimalnumber of battery cells that can be handled via a single IC. While thenumber of serially connected battery cells is a multiple of four in theembodiment, the quantity of serially connected battery cells may notalways be a multiple of four and thus, the numbers of battery cellshandled via the individual ICs may vary within the same system withoutproblem.

Based upon the number of battery cells to be handled via each IC, theserially connected battery cells are divided into a plurality of groups,a specific IC is designated to each group and the IC thus designated toeach of the plurality of groups measures the terminal voltages at thebattery cells constituting the corresponding group. As described above,the numbers of battery cells constituting the individual groups mayvary.

In addition, a communication harness 50, to be used to communicate withthe battery controller 20, is led out from the substrate constitutingthe C/C 80. The communication harness 50 includes a connector disposedat the front end thereof. This connector is connected to a connector(not shown) at the battery controller 20. It is to be noted that whilechip elements such as resistors, capacitors, photocouplers, transistorsand diodes are mounted at the substrate constituting the C/C 80, FIG. 20does not include an illustration of these elements, for purposes ofsimplification. The connectors 48 and 49 are disposed in correspondenceto the two battery assembly blocks at the substrate constituting the C/C80, and the communication harness 50 provided as a member independent ofthe connectors, is also disposed at the substrate so as to enablecommunication with the battery controller 20. Since the connectors 48and 49 and the communication harness 50 are disposed independently ofeach other, maintenance and wiring work is facilitated. In addition, asexplained earlier one of the connectors 48 and 49 is used to connect theserially connected high-voltage side battery cells with the substrateconstituting the C/C 80 and the other connector 48 or 49 is used toconnect the serially connected low-voltage side battery cells with thesubstrate constituting the C/C 80. As a result, the voltage differencemanifesting over the ranges managed via the individual connectors can bereduced. While the state of partial connection, in which only a partialconnection exists momentarily when the connectors are being connected ordisconnected, the adverse effect of such partial connection can bereduced by reducing the voltage difference manifesting over the rangesmanaged via the individual connectors.

The battery assembly blocks 10 and 11 fixed side-by-side at the lowerlid 49 are connected in series via the block connector bus bar (notshown). At the front surface of the lower lid base, an output terminalvia which power from the positive pole high-rate cable 81 and thenegative pole high-rate cable 82 is supplied to an external recipient orpower originating from the outside is received is disposed.

(Diagnosis for Individual Battery Cell)

The measurement of the voltages at the individual battery cells and theover-charge/over-discharge diagnosis operation, executed as the internalprocessing at each of the integrated circuits 3A, . . . , 3M, . . . and3N in FIG. 1, are now described. At the stages STGCV1 STGCV6 indicatedin row 260Y1 in the operation table 260 presented in FIG. 4, theterminal voltages at the individual battery cells are taken in anddiagnosis is executed. As explained earlier, during the measurementphase of the stage STGCV1, the selection circuit 120 in FIG. 6 selectsVCC(V1) and VC2(V2). Through this operation, the terminal voltage at thebattery cell BC1 in FIG. 2 is selected and the selected terminal voltageis input to the voltage detection circuit 122A via the differentialamplifier 262 having a potential shift function. The measurement valuethus input is converted to a digital value at the voltage detectioncircuit 122A and the averaging circuit 264 calculates the average valueby using a predetermined number of measurement values indicating mostrecent measurement results, including the current measurement results.The average value thus calculated is held at a register CELL1 in thecurrent value storage circuit 274.

Based upon the measurement value held at the register BC1 in the currentvalue storage circuit 274, diagnosis for the battery cell BC1 isexecuted to determine whether or not the battery cell BC1 is in anover-charged state or an over-discharged state during the measurementphase of the stage STGCV1 in FIG. 4. Before starting this diagnosis, thereference values to be used in the diagnosis are transmitted from thebattery controller 20 to each integrated circuit where the over-chargediagnosis reference OC is held at a register in the reference valuestorage circuit 278 and the over-discharge diagnosis reference OD isalso held at a register in the reference value storage circuit 278. Inaddition, even when the reference values cannot be transmitted from thebattery controller 20 in response to a communication command 292 or whenerroneous values become held in the reference value storage circuit 278due to noise or the like, an over-charge reference value OCFFO thatcannot be overwritten with a communication command 292, is held inadvance so as to enable detection of an abnormal state attributable toan over-charge.

(Overcharge Diagnosis)

Following the terminal voltage measurement at the stage STGCV1, theterminal voltage value having been obtained through the measurement iscompared with the over-charge decision-making value OC by the digitalcomparator circuit 270. Namely, the measurement value held at theregister BC1, among the plurality of measurement values held at theregisters BC1˜BCG, the VDD values held at the VDD register and thereference power value (PSBG) in the current value storage circuit 274,is selected with a selection signal generated via the decoder 257 andthe decoder 259 based upon the outputs from the first stage counter 256and the second stage counter 258 shown in FIG. 4. The selectedmeasurement value is then input to the digital comparator circuit 270.Likewise, the over-charge diagnosis reference value OC among theplurality of reference values held in the reference value storagecircuit 278 is selected with a selection signal generated via thedecoder 257 and the decoder 259 and the digital comparator circuit 270compares the measurement value corresponding to the battery cell BC1held at the register BC1 with the over-charge diagnosis reference valueOC. If the measurement value obtained at the battery cell BC1 is greaterthan the over-charge diagnosis reference value OC, the digitalcomparator circuit 270 outputs comparison results indicating anabnormality. A digital multiplexer 282 selects a storage location atwhich the output from the digital comparator circuit 270 is to be storedby using a selection signal generated via the decoder 257 and thedecoder 259. If the diagnosis results for the battery cell BC1 indicatean abnormality, the diagnosis results indicating the abnormality areheld in a register diagnosis flag and a register OC flag in the flagstorage circuit 284. Namely, the diagnosis flag and the OC flag are set.The abnormality flag is output from the terminal FFO of the integratedcircuit and is transmitted to the battery controller 20.

Next, in order to assure better reliability, the digital comparatorcircuit 270 compares the measurement value corresponding to the batterycell BC1 with the over-charge diagnosis reference value OCFFO. If themeasurement value obtained in correspondence to the battery cell BC1 isgreater than the over-charge diagnosis reference value OCFFO, it isjudged that an over-charge abnormality has occurred and the abnormalitydiagnosis results are held at the register diagnosis flag and a registerOC flag in the flag storage circuit 284. The abnormality flag set at theflag storage circuit 284 is then transmitted to the battery controller20, as in the situation described earlier. The over-charge diagnosisreference value OCFFO is a reference value that cannot be overwritten bythe battery controller 20. Thus, since the over-charge diagnosisreference value OCFFO remains unchanged even in the event of anabnormality occurring in the program or the operation of the batterycontroller 20, a highly reliable judgment is assured. While theover-charge diagnosis reference value OC, which can be adjusted by thebattery controller 20, enables fine tuning of the decision-makingprocess, the over-charge diagnosis reference value OCFFO is highlyreliable data that are sustained unaltered regardless of the conditionsof the battery controller 20 or the transmission path, as describedabove. Consequently, highly reliable diagnosis is assured through theuse of the two different types of data.

(Over-Discharge Diagnosis)

During the measurement phase at the stage STGCV1, an over-dischargediagnosis is next executed for the battery cell BC1. The digitalcomparator circuit 270 compares the measurement value indicating theterminal voltage at the battery cell BC1, which is stored at theregister BC1 in the current value storage circuit 274, with thereference value OD held in the reference value storage circuit 278. Ifthe measurement value obtained at the battery cell BC1 is less than thereference value OD in the reference value storage circuit 278, thedigital comparator circuit 270 judges that an abnormality has occurredand outputs an abnormality signal. The digital multiplexer 282 selectsthe diagnosis flag and the OD flag in the flag storage circuit 284 byusing a selection signal generated based upon the outputs from thedecoders 257 and 259 and the abnormality signal thus output from thedigital comparator circuit 270 is set at the register diagnosis flag andthe register OD flag.

If the diagnosis flag is set through any of the diagnosis stepsdescribed above, the flag is output from the one-bit output terminal FFOvia an OR circuit 288 and is transmitted to the battery controller 20.

The functions of the selection circuit 286 can be altered with acommunication command 292 issued from the battery controller 20 andthus, the specific details of the flag to be output through the terminalFFO can be selectively adjusted. For instance, an over-chargeabnormality alone may be specified as the condition for setting thediagnosis flag in the flag storage circuit 284. In such a case, anover-discharge abnormality diagnosis output from the digital comparatorcircuit 270 is not set in the register diagnosis flag and instead, theOD flag alone is set. The OD flag may then be output or not dependingupon the specific condition setting selected via the selection circuit286. Since the condition setting can be modified from the batterycontroller 20, a higher level of versatility in the control is afforded.

Following the stage STGCV1 in row 260Y1 in the operation table 260 inFIG. 4, the operation enters the stage STGCV2. The selection circuit 120shown in FIG. 6 selects VC2 (V2) and VC3 (V3), thereby selecting theterminal voltage at the battery cell BC2 in FIG. 2. Through an operationsimilar to that having been executed at the stage STGCV1 as describedearlier, the terminal voltage measured at the battery cell BC2 isdigitized via the analog/digital converter 122A, the averaging circuit264 calculates the average of the predetermined number of measurementvalues indicating the most recent measurement results including thecurrent measurement results and the average value thus calculated isheld at the register BC2 in the current value storage circuit 274. Asare the positions at which other measurement values are to be held, theposition at which the measurement results are to be held is selectedbased upon the outputs from the decoder 257 and the decoder 259 shown inFIG. 4.

Then, as in the operation executed at the stage STGCV1, the measurementvalue corresponding to the battery cell BC2 is selected from the currentvalue storage circuit 274 and the over-charge diagnosis reference valueOC at the reference value storage circuit 278 is selected based upon theoutputs from the decoders 257 and 259 shown in FIG. 4. The diagnosis isthen executed as the digital comparator circuit 270 compares themeasurement value with the over-charge diagnosis reference value. Thedetails of the diagnosis and the specific operational procedure of thediagnosis are identical to those corresponding to the stage STGCV1.

Subsequently, the measurement and the diagnosis are executed at thesucceeding stages STGCV3˜STGCV6 in sequence via the circuit shown inFIG. 6, in much the same way as at the stages STGCV1 and STGCV2.

(SOC Adjustment and Terminal Voltage Measurement)

As explained earlier, the state of charge SOC of each of the batterycells constituting the battery unit 9 is adjusted through controlwhereby the power held in any battery cell with a significant charge isdischarged via a discharge resistor by controlling the balancingswitches 129A˜129F. The open/close control executed on the balancingswitches 129A˜129F may adversely affect the terminal voltage detectionat the various battery cells. Namely, as the balancing switches 129 inthe circuit shown in FIG. 2 closes, a discharge current will flow viathe corresponding resistors R1˜R4, lowering the accuracy with which theterminal voltages at the battery cells BC1˜BC4 are measured.

The open/close control for the balancing switches 129A˜129F must beexecuted based upon the states of all the battery cells in the batteryunit 9. Accordingly, it is desirable to execute the open/close controlthrough processing executed at the battery controller 20 shown inFIG. 1. In other words, it is desirable to engage the individualintegrated circuits 3A˜3N in the control of the balancing switches129A˜129F in response to a command issued by the battery controller 20.At the same time, it is desirable that the integrated circuits 3A˜3Neach individually measure the terminal voltages at the battery cells inthe corresponding group and that they each promptly transmit theterminal voltage measurement values having been obtained through themeasurement and held therein in response to a measurement valuetransmission instruction issued from the battery controller 20. Thismeans that the control for the balancing switches 129A˜129F and thecontrol on the battery cell terminal voltage measurement, executed viadifferent circuits, must be coordinated so as to ensure that the twotypes of control are executed in an integrated manner.

In reference to FIGS. 21 through 25, specific structures that may beadopted to execute the two types of control in an optimal manner areexplained. Since it is desirable to effectively eliminate the adverseeffect of noise in actual products with capacitors C1˜C6 installed inaddition to the discharge resistors R1˜R4 shown in FIGS. 1 and 2, thestructures shown in FIGS. 21 and 22 each include noise removalcapacitors added to the circuit structure shown in FIG. 1 or FIG. 2. Itis to be noted that while four battery cells constitute each batterycell group in the structures illustrated in FIGS. 1 and 2, thestructures illustrated in FIGS. 21 and 22 include six battery cellsconstituting a battery cell group. It is also to be noted that theresistors and the capacitors are installed in the cell controllerindicated by the dotted line 80, together with the integrated circuitalso indicated by the dotted line and that they are connected with therespective battery cells BC1˜BC6 in the battery block via thecommunication harness 50 shown in FIG. 20. FIG. 22 shows a circuitdesigned to further reduce the adverse effect of noise by utilizing thedischarge resistors R1˜R6 shown in FIG. 21. FIGS. 23 and 24 eachillustrate the measurement control operation and the discharge controloperation executed to adjust the states of charge (SOCs). FIG. 23illustrates the operation executed at the circuit shown in FIG. 21,whereas FIG. 24 illustrates the operation executed at the circuit shownin FIG. 22. In addition, FIG. 25 shows a circuit that may be used toenable the control shown in FIG. 23 or FIG. 24.

In the circuit shown in FIG. 21, the terminal voltage at the batterycell BC1 is measured at the stage STGCV1 and then the terminal voltageat the battery cell BC2 is measured at the succeeding stage STGCV2.Subsequently, the terminal voltages at the battery cells BC3˜BC6 aremeasured in sequence. By repeatedly measuring the terminal voltages inthis manner, the levels of the terminal voltages at the battery cellscan be monitored at all times.

For instance, assuming that the balancing switch 129B is in the closedstate in order to adjust the SOC, a discharge current is flowing via thebalancing switch 129B and the resistor R2 and, as the discharge currentaffects the internal resistance and wiring resistance at the batterycell BC2, the voltage VC2 input to the selection circuit 120 assumes avalue lower than that of the terminal voltage measured when thebalancing switch 129B is in the open state. In other words, the lowerterminal voltage value input to the selection circuit 120 when thebalancing switch 129B is in the closed state is bound to reduce themeasurement accuracy.

In order to maintain the measurement accuracy at an acceptable level,the terminal voltage at the battery cell BC1 is measured with thebalancing switch 129A set in the open state by temporarily stopping thecontrol for the SOC of the battery cell BC1 at the stage STGCV1, duringwhich the terminal voltage at the battery cell BC1 is measured, as shownin FIG. 23. At the stage STGCV2 during which the terminal voltage at thenext battery cell BC2 is measured, the terminal voltage at the batterycell BC2 is measured with the balancing switch 129B set in the openstate by temporarily stopping the SOC control for the battery cell BC2.Subsequently, the terminal voltages at the succeeding battery cells aremeasured in sequence with the corresponding balancing switches 129C˜129F(BSW3˜BSW6 in FIG. 23) set in the open state.

The control for the SOC adjustment may be stopped during the measurementphases at the stages STGCV1˜STGCVG. Alternatively, the control for theSOC adjustment may be stopped only briefly while the terminal voltage isactually being measured during each of the stages STGCV1˜STGCV6.

Next, the circuit shown in FIG. 22 is described. Significant noise ispresent in the power lines through which power is supplied from theserially connected battery cells BC1 BC6 to the inverter. In order toreduce the adverse effect of this noise, the circuit shown in FIG. 22includes resistors RA1˜RA7 inserted between the battery cell terminalsand the input end of the selection circuit 120. The resistors RA1˜RA7,together with the capacitors C1˜C7 remove noise, thereby protecting theintegrated circuit from the noise.

As the balancing switch 129A in the circuit shown in FIG. 22 is closedin order to adjust the SOC, the discharge current for the battery cellBC1 flows through the resistor R1, the balancing switch 129A and theresistor RA2. The discharge current flowing through the resistor RA2while the balancing switch 129A is in the closed state is bound toaffect the measurement of the terminal voltage at the battery cell BC2as well as the measurement of the terminal voltage at the battery cellBC1. For this reason, the terminal voltage at the battery cell BC2 mustbe measured by opening both the balancing switch 129A and the balancingswitch 129B. Likewise, the terminal voltage at the battery cell BC3 mustbe measured by opening both the balancing switch 129B and the balancingswitch 129C and the terminal voltages at all the succeeding batterycells have to be measured by opening two balancing switches.

FIG. 24 shows how the balancing switches 129 in the circuit shown inFIG. 22 may be forcibly set in the open state for battery cell terminalvoltage measurement. At the stage STGCV2 during which the terminalvoltage at the battery cell CB2 in FIG. 22 is measured, the SOCadjustment control via the balancing switches 129A and 129B is stopped,and the balancing switches 129A and 129B are sustained in the openstate. At this time, the SOC adjustment control via the balancingswitches 129A and 129B may be stopped over the entire period of thestage STGCV2 or the SOC adjustment control via the balancing switches129A and 129B maybe only briefly stopped while the voltage is actuallybeing measured during the stage STGCV2. This principle is similar tothat having been explained in reference to FIG. 23.

FIG. 24 also shows that at the stage STGCV3 during which the terminalvoltage at the battery cell B3 in FIG. 22 is measured, the SOCadjustment control via the balancing switches 129B and 129C is stopped,and the balancing switches 129B and 129C are sustained in the open statewhile the measurement of the terminal voltage is underway. At this time,the SOC adjustment control via the balancing switches 129B and 129C maybe stopped over the entire period of the stage STGCV3 or the SOCadjustment control via the balancing switches 129B and 129C may be onlybriefly stopped while the voltage is actually being measured during thestage STGCV3, as described above.

At the stages STGCV4 and STGCV5, the balancing switches 129C and 129Dand the balancing switches 129D and 129E are respectively sustained inthe open state while measuring the terminal voltages at the batterycells BC4 and BC5. At the stage STGCV6, the terminal voltage at thebattery cell BC6 is measured. While the terminal voltage at the batterycell BC6 is being measured, the balancing switch 129F is sustained inthe open state.

It is to be noted that the balancing switches 129A˜129F are eachcontrolled for purposes of the SOC adjustment during the period of timeindicated by ⇄ in FIGS. 23 and 24. In addition, during the period oftime marked as “OFF”, the control of the corresponding balancing switchamong the balancing switches 129A˜129F, executed for purposes of SOCadjustment is halted with the balancing switch forcibly set in the openstate. By forcibly opening the corresponding balancing switches 129 soas to give priority to the battery cell terminal voltage measurementover the SOC adjustment control executed via the battery control 20 asdescribed above, the battery cell terminal voltages can be measured withbetter accuracy.

Next, in reference to the circuit diagram presented in FIG. 25, theoperation executed to open the balancing switches 129 is described.First, the control value to be used in the SOC adjustment is calculatedin step 815 in FIG. 14 and the calculation results indicating thecontrol value are transmitted to the individual integrated circuits 3A,. . . , 3M, . . . and 3N as a communication command 292. Thecommunication circuit 127 shown in FIG. 2 or FIG. 7 of each of theintegrated circuits 3A, . . . , 3M, . . . and 3N receives thetransmitted control value and the balancing switches 129A˜129Farecontrolled based upon the control value thus received.

Data 330 in FIG. 25 correspond to the data 330 in the reception register322 shown in FIG. 7 and the contents of the data 330 are input todischarge control circuits 1321˜1326. The control signal input to thedischarge control circuits indicates either “1” or “0”. The controlsignal indicating “1” is an instruction for control under which thecorresponding battery cell is discharged by closing the balancing switch129, whereas the control signal indicating “0” is an instruction forcontrol under which the balancing switch 129 remains open and thus thebattery cell is not discharged. Such a control signal is held at each ofthe discharge control circuit 1321˜1326 and the balancing switches129A˜129F are individually controlled based upon the data held at therespective discharge control circuits.

The data held at the discharge control circuits 1321˜1326 are providedto AND gates 12˜62 and are used to drive the balancing switches129A˜129F via OR gates 11˜61. If control for a specific balancing switchamong the balancing switches 129A˜129F is to be given priority over theSOC adjustment control, the signal indicating the data held at thecorresponding discharge control circuit among the discharge controlcircuits 1321˜1326 is cut off at the corresponding AND gate among theAND gates 12˜62. During this cutoff period, which is to be described inreference to FIGS. 29 and 30, the terminal voltage at the correspondingbattery cell is measured based upon the outputs from the decoder 257 andthe decoder 259 and a control-off signal is transmitted from a circuit2802 to the specific AND gate among the AND gates 12˜62 based upon theoutputs from the decoders 257 and 259.

While the SOC adjustment control for a given battery cell is halted witha specific AND gate among the AND gates 12˜62 set in the open state, thecorresponding AND gate among AND gates 11˜61 is closed and thecorresponding balancing switch among the balancing switches 129A˜129F isdriven based upon the output from the corresponding OR gate among ORgates 12˜62. In other words, while a given AND gate among the AND gates12˜62 is in the open state and the corresponding AND gate among the ANDgates 11˜61 is in the closed state, a control signal to be used tocontrol the balancing switch among the balancing switches 129A˜129F canbe output from the corresponding measurement control circuit amongmeasurement control circuits 2811˜2861 so as to assure optimalmeasurement. In addition, when executing abnormality diagnosis for thedetection harness 32, which is to be detailed later, the diagnosiscontrol circuits 2812˜2862 output a control signal to control therespectively balancing switches 129A˜129F.

As described above, the integrated circuits 3A, . . . 3M, . . . and 3Neach include a dedicated circuit via which a specific balancing switchamong the balancing switches 129A˜129F is controlled while the SOCadjustment control is halted to give priority to the measurementoperation. As a result, accurate measurement and diagnosis are enabled.

(Diagnosis for the ADC, the Differential Amplifier 262 and the ReferenceVoltage)

At the stage STG “reference power” in row 260Y1 in the operation table260 presented in FIG. 4, a diagnosis for the internal reference voltage,the analog circuit and the voltage detection circuit 122A is executed. Asource voltage to be used to engage the analog circuit and the digitalcircuit shown in FIG. 6 in operation is generated at a power sourcecircuit 121 (see FIG. 2) within the integrated circuit. If the sourcevoltage is generated based upon an absolute reference power level, aprecise source voltage can be obtained with relative ease. However, ifthe absolute reference voltage changes, the source voltage, too, maychange.

At the stage STG “reference power”, the diagnosis for the referencepower and the diagnosis for the analog circuit and the voltage detectioncircuit 122A are executed with a high level of efficiency. The operationexecuted at the stage STG “reference power” is described below in morespecific terms.

The input circuit 116 included in the circuit structure shown in FIG. 6select the reference power and the GND. The voltage representing thedifference between the potentials at the GND and the reference powerthus selected is input to the differential amplifier 262, where thescale is adjusted in correspondence to the potential shift. The voltagevalue is then input to the analog/digital converter 122A. At theanalog/digital converter 122A, the input signal is converted to adigital value and the digital signal is held as data PSBG at a PSBGregister in the current value storage circuit 274 based upon the outputsfrom the decoders 257 and 259.

As long as the relevant circuit operates in the normal state, thevoltage at the reference power assumes a known value. Accordingly, alower limit value for the reference power assuming a slightly lowervalue than the known voltage value of the reference power and an upperlimit value for the reference power, assuming a slightly larger valuethan the known voltage value of the reference power, are respectivelyheld in a lower limit value save area and an upper limit value save areadesignated in advance at a register in the reference value storagecircuit 278. Under normal circumstances, the voltage at the referencepower assumes a value between the lower limit value and the upper limitvalue for the reference power. Even when the voltage at the referencepower is within the normal range, the output from the analog/digitalconverter 122A will indicate a value outside the normal range unless theanalog circuit operates in the normal states, e.g., unless thedifferential amplifier 262 operates in the normal state. In addition, anabnormality occurring at the analog/digital converter 122A will alsoresult in the output from the analog/digital converter 122A indicating avalue outside the normal range.

Accordingly, a diagnosis is executed by engaging the digital comparatorcircuit 270 in comparison operation in order to determine if the“reference power” value held in the current value storage circuit 274 isbetween the reference power lower limit value and the reference powerupper limit value held in the reference value storage circuit 278.

Based upon the outputs from the decoders 257 and 259, the digitalmultiplexer 272 selects the measurement value “reference power” andtransmits the selected measurement value to the digital comparatorcircuit 270. In addition, based upon the outputs from the decoders 257and 259, the digital multiplexer 272 selects the reference power lowerlimit value and transmits the selected value to the digital comparatorcircuit 270. The digital comparator circuit 270 judges that anabnormality has occurred if the measurement value “reference power” issmaller than the reference power lower limit value and, accordingly, anabnormality flag is set at the abnormality flag holding registerselected by the digital multiplexer 282 based upon the outputs from thedecoders 257 and 259, i.e., at the register diagnosis flag in the flagstorage circuit 284 in the embodiment. If, on the other hand, themeasurement value “reference power” is greater than the reference powerlower limit value, the current state is judged to be normal and,accordingly, no abnormality flag is set in the flag storage circuit 284.

In addition, during the stage STG “reference power” the digitalmultiplexer 272 selects the measurement value “reference power” basedupon the outputs from the decoders 257 and 259 and transmits theselected measurement value to the digital comparator circuit 270. Inaddition, based upon the outputs from the decoders 257 and 259, thedigital multiplexer 272 selects the reference power upper limit valueand transmits the selected value to the digital comparator circuit 270.The digital comparator circuit 270 judges that an abnormality hasoccurred if the measurement value “reference power” is larger than thereference power upper limit value and, accordingly, an abnormality flagis set at the abnormality flag holding register selected by the digitalmultiplexer 282 based upon the outputs from the decoders 257 and 259,i.e., at the register diagnosis flag in the flag storage circuit 284 inthe embodiment. If, on the other hand, the measurement value “referencepower” is smaller than the reference power upper limit value, thecurrent state is judged to be normal and, accordingly, no abnormalityflag is set in the flag storage circuit 284. During the stage STGPSBG,the diagnosis is executed as described above to determine whether or notthe differential amplifier 262, which is an analogue amplifier, and theanalog/digital converter 122A are operating in the normal state, so asto assure a high level of reliability.

(Diagnosis for the Digital Comparator Circuit)

At the stage STGCal in the operation table 260 in FIG. 4, a diagnosisfor the digital comparator circuit is executed. The diagnosis operationis described below. Based upon the outputs from the decoders 257 and259, the digital multiplexer 272 selects an addition calculation value280. The addition calculation value 280 is a value obtained by adding apredetermined value to a reference value, e.g., the reference value OC,held in the reference value storage circuit 278. The digital multiplexer276 selects one of the reference values held in the reference valuestorage circuit 270 such as the reference value OC and inputs theselected reference value to the digital comparator circuit 270 where itis used as a comparison reference. In addition, the addition calculationvalue 280 obtained by adding a predetermined value, e.g., “1”, to theselected reference value OC is input to the digital comparator circuit270 via the digital multiplexer 272. If the digital comparator circuit270 judges that the addition calculation value 280 is greater than thereference value OC, the digital comparator circuit 270 can be assumed tobe operating in the normal state.

Next, the digital multiplexer 272 selects a subtraction calculationvalue 281 based upon the outputs from the decoders 257 and 259. Thesubtraction calculation value 281 is a value obtained by subtracting apredetermined value such as “1” from a reference value, e.g., thereference value OC, held in the reference value storage circuit 278. Thedigital multiplexer 276 selects one of the reference values held in thereference value storage circuit 270 such as the reference value OC andinputs the selected reference value to the digital comparator circuit270 where it is used as a comparison reference. In addition, thesubtraction calculation value 281 obtained by subtracting apredetermined value, e.g., “1”, from the selected reference value OC isinput to the digital comparator circuit 270 via the digital multiplexer272. If the digital comparator circuit 270 judges that the subtractioncalculation value 281 is smaller than the reference value OC, thedigital comparator circuit 270 can be assumed to be operating in thenormal state.

As described above, the reference value OC held in the reference valuestorage circuit 278 is compared with the sum obtained by adding apredetermined value to the reference value OC and with the differenceobtained by subtracting a predetermined value from the reference valueOC, so as to determine whether or not the comparator is operating in thenormal state.

The addition calculation value 280 and the subtraction calculation value281 are used in order to create conditions under which knownrelationships to the comparison reference exist and obtain verifiablecomparison results. For this reason, instead of the values obtained byadding/subtracting a predetermined value to/from the comparisonreference, values obtained by shifting the data toward the higher-orderside and the lower-order side may be utilized. The values obtainedthrough such data shift are equivalent to values obtained by multiplyingthe comparison reference by a predetermined value 4 and subtracting apredetermined value 4 from the comparison reference and thus, knownrelationships to the comparison reference can also be created with thesevalues.

In reference to FIGS. 26 and 27, the diagnosis executed to determinewhether or not an abnormality has occurred at the detection harness 32connecting the positive poles and the negative poles of the batterycells BC to the cell controller 80 is described. It is to be noted thatwhile the circuits in FIGS. 26 and 27 are similar to those shown inFIGS. 1 and 2, they further include noise removal capacitors C1˜C6. Inaddition, while each battery cell group is made up with four batterycells in the circuit structures illustrated in FIGS. 1 and 2, thecircuits shown in FIGS. 26 and 27 include six battery cells constitutinga battery cell group. FIG. 26 illustrates a circuit in which adisconnection has occurred in a harness segment L2 constituting thedetection harness 32 in FIG. 1 or FIG. 2. FIG. 27 shows a circuit inwhich a disconnection has occurred in the harness segment L2constituting the detection harness 32 included in the circuit shown inFIG. 22. Such a disconnection may occur due to poor contact at aconnection area where a given battery cell in FIG. 19 and the detectionharness 32 are connected with each other or a poor connection at theconnector 48 or 49, where the cell controller 80 is connected withindividual harness segments, as shown in FIG. 20. Although not common, adisconnection may also occur at the detection harness 32 itself.

It is essential that any potential abnormality at each battery cell besensed in order to preempt the abnormality. If an abnormality actuallyoccurs in the electrical connection between the battery cell and thecorresponding integrated circuit, the potential abnormality that mayoccur at the battery cell described above can no longer be sensed. Now,in reference to FIG. 28, a method that may be adopted to detect anabnormality occurring in the electrical connection between the batterycell and the integrated circuit, as shown in FIG. 26 or 27, isdescribed. It is to be noted that the basic operation executed in thecircuit shown in FIG. 26 or 27 has already been described. In addition,while an explanation is given below by assuming that a disconnection hasoccurred in the harness segment L2 in the detection harness 32, anabnormality can be detected in a similar manner regardless of whichharness segment among the harness segments L1˜L7 becomes disconnected.

If the harness segment L2 in the detection harness 32 becomesdisconnected while the balancing switches 129A˜129C are in the openstate, the voltage VC2 input to the selection circuit 120 may indicate anormal value close to the terminal voltage V2 at the battery cell due tothe various electrostatic capacitances including that at the capacitorC2, as shown in FIG. 28. Thus, the abnormality cannot be sensed simplybased upon the voltage VC2.

Accordingly, the balancing switch 129B through which the dischargecurrent flows via the diagnosis target harness segment L2 in thedetection harness 32 is closed. As the balancing switch 129B is set inthe closed state, the electrical charge having accumulated in theelectrostatic capacitance including the capacitor C2 present between thecircuits corresponding to the harness segments L2 and L3 in thedetection harness 32 is released, causing a sudden decrease in thevoltage VC2 input to the selection circuit 120. If no disconnection hasoccurred, the electrical current is supplied from the battery cell BC2and thus, the voltage VC2 input to the input circuit 120 hardly changes.

The terminal voltage at the battery cell BC2 is measured (measurement 1)at the terminal voltage measurement stage for the battery cell BC2having been described in reference to FIGS. 23 and 24. As explainedearlier, the balancing switch 129B remains in the open state during thismeasurement phase. Since the electrical charge flowing into theelectrostatic capacitance including the capacitor C2 present between thecircuits of the harness segments L2 and L3 in the detection harness 32is then accumulated at the electrostatic capacitance, the voltage VC2input to the input circuit 120 slightly increases. However, the voltageVC2 measured through the measurement 1 is much lower than the normalvoltage. The voltage VC2 thus measured is held at the register BC2 inthe current value storage circuit 274 shown in FIG. 5.

In the diagnosis for the battery cell BC2 executed in successionfollowing the measurement, diagnosis results indicating an abnormalityare obtained via the digital comparator 270 based upon the measurementvalue read out from the current value storage circuit 274, whichindicates an abnormal value equal to or less than the over-dischargethreshold value OD in the reference value storage circuit 278. Theabnormality diagnosis results are set at the register diagnosis flag inthe flag storage circuit 284. The voltage VC2 assumes a value less thanthe over-discharge threshold value OD in the event of a disconnection.Accordingly, a disconnection threshold value, even smaller than theover-discharge threshold value OD, is set and the digital comparator 270is engaged in comparison of the measurement value held at the registerBC2 in the current value storage circuit 274 with the disconnectionthreshold value. As a result, the decision with regard to whether or nota disconnection has occurred can be made with ease. By using the valueheld at the register OCFFO in the reference value storage circuit 278 inFIG. 6 as the disconnection threshold value, the sensing operation fordisconnection can be executed at all times.

As shown in FIG. 28, as the balancing switch 129B (BSW2) is set in theopen state and then the balancing switches 129A (BSW1) and 129C (BSW3)are set in the closed state, the voltages from the serially connectedbattery cells BC1 and BC2 are both applied to the capacitor C2,significantly raising the terminal voltage at the capacitor C2.Accordingly, immediately after the measurement 1, the balancing switches129A (BSW1) and 129C (BSW3) are both closed and the terminal voltage atthe battery cell BC2 is measured again (measurement 2). The voltage VC2measured at this time is bound to indicate a very high value, farexceeding the over-charge threshold value, thereby enablingdisconnection detection with ease.

As described above, the measurement results obtained through themeasurement 2 are held at the register BC2 in the current value storagecircuit 274 shown in FIG. 6. The measurement value held at the registerBC2 in the current value storage circuit 274 may be compared at thedigital comparator 270 with the disconnection detection threshold valuein order to detect a disconnection, or a disconnection diagnosis mayinstead be executed through software processing executed at the batterycontroller 20.

FIG. 29 illustrates a method for executing the diagnosis in response toa communication command 292 issued from the battery controller 20. Themethod is described by assuming that a disconnection has occurred at theharness segment L2 in the detection harness 32. A disconnectiondiagnosis communication command 292 is transmitted with predeterminedtiming. The communication command 292 indicates a specific diagnosistarget integrated circuit and also contains an instruction “open allbalancing switches 129”. Namely, the data 330 in the communicationcommand 292 indicate “0”, i.e., “open”. In response to the instruction,the instruction target integrated circuit opens the balancing switches129.

Next, a close instructions is transmitted to the balancing switch 129B,thereby closing the balancing switch 129B in order to discharge thebattery cell connected with the diagnosis target detection harness 32with predetermined timing. If the harness segment L2 is disconnected,the input signal VC2 provided to the selection circuit 120 will indicatea value close to 0. Subsequently, before an instruction is output fromthe battery controller 20, the balancing switch 129B enters the openstate and the terminal voltage at the battery cell BC2 is measuredduring the measurement stage, in which the voltage at the battery cellBC2 is measured based upon a stage signal generated in the integratedcircuit. If the harness segment L2 is disconnected, the input signal VC2provided to the selection circuit 120 will indicate a very low voltage,which is then held at the register BC2 in the current value storagecircuit 274 shown in FIG. 6.

Since the integrated circuit independently measures the battery cellterminal voltages over short intervals, the balancing switch 129Breenters the open state quickly and the terminal voltage at the batterycell BC2 is measured. If the harness segment L2 is disconnected, themeasurement results will indicate a very low value which is then held atthe register BC2 in the current value storage circuit 274.

In response to a diagnosis result intake instruction issued from thebattery controller 20, the integrated circuit transmits the measurementresults held at the register BC2 in the current value storage circuit274. The battery controller 20, having received the measurement resultsindicating a value lower than the over-discharge level is able to detectthe disconnection. Namely, the measurement results transmitted from theintegrated circuit are compared with a threshold value ThL1 in FIG. 29and if the measurement results indicate a value lower than the thresholdvalue ThL1, the battery controller judges that a disconnection hasoccurred and proceeds to execute preliminary operation before actuallycutting off the connection between the DC power source constituted withlithium batteries and the inverter. As soon as the preliminaryprocessing is completed, it opens the relays RLP and RLN.

In order to assure even more reliability, the battery controller 20transmits an instruction for closing the balancing switches 129A and129C and opening the balancing switch 129B. In the event of adisconnection, the input voltage VC2 provided to the selection circuit120 increases greatly if the balancing switches 129 disposed on the twosides of the diagnosis target battery cell. Thus, a voltage valuegreater than the over-charge threshold value will be measured. Themeasurement results are then held at the register BC2 in the currentvalue storage circuit 274.

In response to a diagnosis result intake instruction issued from thebattery controller 20, the integrated circuit transmits the measurementvalue to the battery controller 20. The battery controller 20 receivesthe measurement results, compares the received measurement results witha disconnection detection threshold value ThL2, which is greater thanthe over-charge threshold value and if the measurement results indicatea value greater than the threshold value ThL2, the battery controller 20judges that a disconnection has occurred. While accurate disconnectiondetection is enabled simply by comparing the results obtained throughthe measurement 1 or the measurement 2 with the threshold value ThL1 orthrough comparison of the average of the measurement values obtainedthrough the measurement 1 and the measurement 2 with the threshold valueThL1, the accuracy of the disconnection detection is further enhanced byalso comparing the measurement results with the threshold value ThL2, asdescribed above.

By adopting the embodiment described above, highly accuratedisconnection detection is enabled.

In addition, highly efficient disconnection detection is enabled byusing the measurement values obtained through regular battery cellterminal voltage measurement operation.

Furthermore, since the diagnosis is executed by using the existingbalancing switches 129 used to control the SOCs, without having toinstall additional special circuits, the simplicity of the circuitstructure is maintained.

Next, in reference to FIGS. 30˜32, a method that may be adopted toenable each integrated circuit to automatically execute a disconnectiondiagnosis is described. The disconnection diagnosis can be automaticallyexecuted by measuring battery cell terminal voltage based upon the stagesignal, as shown in FIG. 4. FIG. 30 indicates a specificmeasurement/diagnosis schedule, whereas FIG. 32 shows a specific circuitstructure.

In the upper row in FIG. 30, the measurement and the disconnectiondiagnosis executed in the integrated circuit 3A in cycle m and cycle m+lin response to stage signals are indicated. The measurement and thedisconnection diagnosis executed in the integrated circuit 3B succeedingthe integrated circuit 3A are indicated in the middle row, whereas themeasurement and the disconnection diagnosis executed in the integratedcircuit 3C succeeding the integrated circuit 3B are indicated in thelower row. The integrated circuits 3B and 3C individually start thestage processing shown in FIG. 4, in response to a synchronous signalprovided from the integrated circuit 3A and a synchronous signalprovided from the integrated circuit 3B respectively. It is to be notedthat during a period marked “ON” in FIG. 30, control for sustaining thecorresponding balancing switch 129 in the closed state is underway.During a period marked “OFF”, control under for sustaining the balancingswitch 129 in the open state is underway. “measurement” indicates aperiod during which control for the battery cell terminal voltagemeasurement and the disconnection diagnosis is underway. During anyperiod of time that is not marked as “ON”, “OFF” or “measurement”, theSOC adjustment control is underway.

At the stage STGCal, the balancing switch 129A is set in the closedstate in the integrated circuit 3A. If the detection harness 32 isdisconnected, the voltage input to the selection circuit 120 will assumea very small value, with the balancing switch 129A set in the closedstate, as has been explained in reference to FIG. 28. As a result, theanalog/digital converter 122A in FIG. 31 detects the terminal voltage atthe battery cell BC1, measured at the stage STGCV1, indicating anexcessively small value. Consequently, the measurement results held atthe register BC1 in the current value storage circuit 274 will indicatean extremely small value. It is to be noted that control is executed tosustain the balancing switch 129B, too, in the open state, in order toimprove the measurement accuracy in the stage STGCV1.

In the disconnection diagnosis executed following the measurement, thedigital comparator 270 compares the measurement value held at theregister BC1 in the current value storage circuit 274 with thedisconnection diagnosis threshold value ThL1 held in the reference valuestorage circuit 278. If the measurement value held at the register BC1is less than the disconnection diagnosis threshold value ThL1, it isjudged that an abnormality attributable to a disconnection has occurredand accordingly, the diagnosis flag in the flag storage circuit 284 isset to “1”. As has already been explained in reference to FIG. 6, thediagnosis flag setting selected at this time is immediately reported tothe battery controller 20. It is to be noted that the basic operationexecuted in the circuit shown in FIG. 31 is similar to that having beendescribed in reference to FIG. 6 and the like.

Unless an abnormality such as a disconnection exists, the terminalvoltage at the battery cell BC1 measured at the stage STGCV1 indicates anormal value and, accordingly, no abnormality is detected through thediagnosis executed via the digital comparator 270. In cycle m in FIG.30, the terminal voltage measurement and the diagnosis are executed onlyfor the odd-numbered battery cells. Following the terminal voltagemeasurement and the diagnosis for the battery cell BC1, the terminalvoltage measurement and the disconnection diagnosis are executed for thebattery cell BC3. At the stage STGCV2, the balancing switch 129Ccorresponding to the battery cell BC3 is first closed and then thebalancing switch 129C is set back into the open state at the stageSTGCV3 to measure the terminal voltage at the battery cell BC3. Thedigital comparator 270 shown in FIG. 31 executes the disconnectiondiagnosis as has been explained earlier. In order to improve theaccuracy with which the terminal voltage at the battery cell BC3 isdetected and the disconnection diagnosis for the battery cell BC3 isexecuted at the stage STGCV3, the balancing switches 129B and 129Ddisposed on the two sides of the balancing switch 129C are sustained inthe open state as has been explained in reference to FIG. 30.

Likewise, the balancing switches 129D and 129F are sustained in the openstate at the stage STGCV5, in order to measure the terminal voltage atthe battery cell BC3 and execute the disconnection diagnosis for thebattery cell BC3. The measurement and the diagnosis are executed for theodd-numbered battery cells BC1, BC3 and BC5 as described above. Themeasurement and the diagnosis for the even-numbered battery cells BC2,BC4 and BC6 are executed in a similar manner in the next cycle m+1. Inshort, in the operation executed as indicated in the schedule presentedin FIG. 30, the measurement and the diagnosis for the odd-numberedbattery cells and the even-numbered battery cells are executed indifferent stage cycles.

When executing the measurement and the diagnosis for the battery cellBC1 at the stage STGCV1 in the integrated circuit 3B, the balancingswitch 129F in the preceding integrated circuit 3A must be sustained inthe open state. Accordingly, a synchronous signal is transmitted fromthe integrated circuit 3A to the integrated circuit 3B which thengenerates a stage signal in synchronization with the synchronous signalfrom the integrated circuit 3A. In the embodiment, the integratedcircuit 3B, having received the synchronous signal from the integratedcircuit 3A, starts generating the first stage signal STGCal.

One of the two adjacent integrated circuits transmits a synchronoussignal to the other integrated circuit over a predetermined cycle andthe other integrated circuit, having received the synchronous signal,starts generating a specific stage signal. As a result, while themeasurement for the battery cell in the preceding integrated circuit,i.e., the measurement for the battery cell BC6 corresponding to theintegrated circuit 3A, is underway, the balancing switch 129Acorresponding to the battery cell BC1 in the succeeding integratedcircuit 3B is sustained in the open state. In addition, while themeasurement for the battery cell BC1 in the succeeding integratedcircuit 3B is underway, the balancing switch 129F corresponding to thebattery cell BC6 in the preceding integrated circuit 3A is sustained inthe open state.

FIG. 30 indicates that an operation similar to that described above isexecuted in the integrated circuits 3B and 3C and a synchronous signalis transmitted from the integrated circuit 3B to the integrated circuit3C as the integrated circuit 3B executes the operation at a specificstage. This structure assures that accurate measurement and accuratediagnosis are executed by sustaining the balancing switches 129,corresponding to the battery cells on the two sides of the measurementtarget battery cell, connected in series with the measurement targetbattery cell, in the open state.

While the circuit shown in FIG. 32 is similar to the circuit shown inFIG. 1, it further includes a transmission path 56 through which asynchronous signal is transmitted. Otherwise, the circuit structureadopted therein and the operation executed therein are similar to thosedescribed in reference to FIG. 1. As shown in FIG. 32, a synchronoussignal is transmitted from a synchronous signal output end SYNO of theintegrated circuit 3A to a synchronous signal input end SYNI of theintegrated circuit 3B. Likewise, a synchronous signal is transmittedfrom a synchronous signal output end SYNO of the integrated circuit 3M-1to a synchronous signal input end SYNI of the integrated circuit 3M andso forth. Finally a synchronous signal is transmitted from thesynchronous signal output end SYNO of the integrated circuit 3N-1 to asynchronous signal input end SYNI of the integrated circuit 3N.

While the synchronous signal is transmitted from an integrated circuitassuming a higher potential to the next integrated circuit assuming alower potential in the circuits shown in FIGS. 30 and 32, this is simplyan example and the synchronous signal may instead be transmitted from anintegrated circuit with a lower potential to the next integrated circuitwith a higher potential, as long as stage signals are generated insynchronization with each other within the integrated circuits disposednext to each other.

The disconnection diagnosis can be executed with ease via the balancingswitches 129 as described above.

The embodiments described above may be adopted by themselves or incombination. The advantages of the individual embodiments may berealized independently of one another or synergistically throughcombination thereof. In addition, the present invention may be embodiedin any way other than those described in reference to the embodiments,as long as the features characterizing the present invention remainintact.

1. An automotive power supply system comprising: a battery module thatincludes a plurality of serially connected battery groups eachconstituted with a plurality of serially connected battery cells; aplurality of integrated circuits each disposed in correspondence to oneof the battery groups; a control circuit; a transmission path throughwhich the integrated circuits are connected to the control circuit; anda relay circuit via which an electrical current is supplied from thebattery module, wherein: in response to a start signal instructing anoperation start and received via the transmission path, each integratedcircuit measures terminal voltages at the battery cells in thecorresponding battery group and executes an abnormality diagnosis; andif abnormality diagnosis results provided by the integrated circuitsindicate no abnormality, the control circuit closes the relay, enablingsupply of electrical current from the battery module and subsequently,the control circuit receives measurement results from the integratedcircuits via the transmission path.
 2. An automotive power supply systemaccording to claim 1, wherein: the integrated circuit cyclicallygenerates a selection signal to be used to measure the battery cellsconstituting the corresponding battery group in a predetermined order;and the integrated circuit includes a selection circuit that selects aterminal voltage to be measured based upon the selection signal, ananalog/digital converter that converts the selected terminal voltage toa digital value and a digital comparator circuit that executes anabnormal state diagnosis based upon the digital value resulting fromconversion executed at the analog/digital converter, and transmits asignal indicating an abnormality to the control circuit if diagnosisresults indicate an abnormal state.
 3. An automotive power supply systemaccording to claim 1, wherein: the control circuit transmits the startsignal to each integrated circuit upon receiving a signal generatedbased upon an operation of a key switch at a vehicle.
 4. An automotivepower supply system according to claim 1, wherein: the integratedcircuit includes a one-bit signal transmission/reception circuit and aserial signal transmission/reception circuit and transmits a signalindicating an abnormality from the one -bit signal transmission circuitupon detecting an abnormality.
 5. An automotive power supply systemcomprising: a lithium battery module that includes a plurality ofserially connected lithium battery groups each constituted with aplurality of serially connected lithium battery cells; a plurality ofintegrated circuits each disposed in correspondence to one of thelithium battery groups in the battery module; a transmission paththrough which the integrated circuits are connected; and a relay viawhich power is supplied from the lithium battery module, wherein: theintegrated circuit cyclically generates a stage signal to be used tospecify a measurement target lithium battery cell in response to anoperation start signal; and the integrated circuit includes: a selectioncircuit that selects the measurement target lithium battery cell in thelithium battery group corresponding to the integrated circuit based uponthe stage signal; an analog/digital converter that converts a terminalvoltage at the lithium battery having been selected by the selectioncircuit to a digital value; a digital comparator circuit that comparesthe digitized terminal voltage value with an over-charge diagnosisthreshold value; and a transmission circuit that outputs an abnormalitysignal indicating an abnormality based upon comparison results providedfrom the digital comparator circuit and includes a one-bit signaltransmission terminal used to transmit the abnormality signal, a one-bitsignal reception terminal, a serial transmission terminal and a serialreception terminal.